Reflective mask blank, method of manufacturing same, reflective mask and method of manufacturing semiconductor device

ABSTRACT

A reflective mask blank capable of facilitating the discovery of contaminants, scratches and other critical defects by inhibiting the detection of pseudo defects attributable to surface roughness of a substrate or film in a defect inspection using a highly sensitive defect inspection apparatus. The reflective mask blank has a mask blank multilayer film comprising a multilayer reflective film, obtained by alternately laminating a high refractive index layer and a low refractive index layer, and an absorber film on a main surface of a mask blank substrate, wherein, in the relationship between bearing area (%) and bearing depth (nm) as measured with an atomic force microscope for a 1 μm×1 μm region of the surface of the reflective mask blank on which the mask blank multilayer film is formed, the surface of the reflective mask blank satisfies the relationship of (BA 70 −BA 30 )/(BD 70 −BD 30 )≧60(%/nm) and maximum height (Rmax)≦4.5 nm.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2014/072689 filed Aug. 29, 2014, claiming priority based onJapanese Patent Application No. 2013-193070 filed Sep. 18, 2013, thecontents of all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a reflective mask blank thatfacilitates discovery of contaminants or scratches and other criticaldefects by inhibiting pseudo defects attributable to surface roughnessof a substrate or film in a defect inspection using a highly sensitivedefect inspection apparatus, a method of manufacturing the reflectivemask blank, a reflective mask using the reflective mask blank and amethod of manufacturing a semiconductor device using such reflectivemask.

BACKGROUND ART

Accompanying the increasingly higher levels of integration ofsemiconductor devices in the semiconductor industry in recent years,there is a need for fine patterns that exceed the transfer limitationsof conventional photolithography methods using ultraviolet light.Extreme ultraviolet (EUV) lithography is considered to be a promisingexposure technology that uses EUV light to enable the formation of suchfine patterns. Here, EUV light refers to light in the wavelength band ofthe soft X-ray region or vacuum ultraviolet region, and morespecifically, light having a wavelength of about 0.2 nm to 100 nm.Reflective masks have been proposed as transfer masks for use in EUVlithography. Such reflective masks have a multilayer reflective filmthat reflects exposure light formed on a substrate, and an absorber filmformed in a pattern on the multilayer reflective film that absorbsexposure light.

The reflective mask is manufactured from a substrate, a multilayerreflective film formed on the substrate, and a reflective mask blankhaving an absorber film formed on the multilayer reflective film, byforming an absorber film pattern by photolithography and the like.

As described above, due to the growing demand for miniaturization in thelithography process, significant problems are being encountered in thelithography process. One problem relates to defect information of maskblank substrates, substrates with multilayer reflective films andreflective mask blanks and the like used in the lithography process.

Mask blank substrates are being required to have even higher smoothnessfrom the viewpoints of improving defect quality accompanying theminiaturization of patterns in recent years and the optical propertiesrequired of transfer masks.

In addition, substrates with multilayer reflective films are also beingrequired to have even higher smoothness from the viewpoints of improvingdefect quality accompanying the miniaturization of patterns in recentyears and the optical properties required of transfer masks. Multilayerreflective films are formed by alternately laminating layers that have ahigh refractive index with layers that have a low refractive index onthe surface of a mask blank substrate. Each layer is typically formed bysputtering using sputtering targets composed of the materials that formthese layers.

Ion beam sputtering is preferably used as the sputtering method from theviewpoint of not requiring the generation of plasma by electricaldischarge and being resistant to contamination by impurities present inthe multilayer reflective film, and from the viewpoint of having anindependent ion source thereby making setting of conditionscomparatively easy. In addition, from the viewpoint of the smoothnessand surface uniformity of each layer formed, the high refractive indexlayer and low refractive index layer are deposited by allowing sputteredparticles to reach the target at a large angle with respect to thenormal (line perpendicular to the main surface of the mask blanksubstrate) of a main surface of the mask blank substrate, or in otherwords, at an angle diagonal or nearly parallel to a main surface of thesubstrate.

Patent Literature 1 describes a technology for manufacturing a substratewith a multilayer reflective film using such a method in which, whendepositing a multilayer reflective film of a reflective mask blank forEUV lithography on a substrate, ion beam sputtering is carried out bymaintaining the absolute value of an angle α formed between the normalof the substrate and sputtered particles entering the substrate suchthat 35 degrees≦α≦80 degrees while rotating the substrate about thecentral axis thereof.

In addition, Patent Literature 2 describes a reflective mask blank forEUV lithography in which an absorber layer that absorbs EUV lightcontains Ta, B, Si and N, the content of B is not less than 1 at % toless than 5 at %, the content of Si is 1 at % to 25 at %, and thecomposition ratio between Ta and N (Ta:N) is 8:1 to 1:1.

PRIOR ART LITERATURE Patent Literature

Patent Literature 1: JP 2009-510711A

Patent Literature 2: JP 2007-311758A

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Accompanying the rapid pace of pattern miniaturization in lithographyusing EUV light, the defect size of reflective masks in the form of EUVmasks is becoming increasingly smaller year by year, and the inspectionlight source wavelengths used during defect inspections in order todiscover such fine defects are approaching the light source wavelengthof the exposure light.

For example, highly sensitive defect inspection apparatuses having aninspection light source wavelength of 266 nm (such as the “MAGICS M7360”Mask/Substrate/Blank Defect Inspection Apparatus for EUV Exposuremanufactured by Lasertec Corp.), an inspection light source wavelengthof 193 nm (such as the “Teron 610” of “Teron 600 Series” EUV Mask/BlankDefect Inspection Apparatuses manufactured by KLA-Tencor Corp.), or aninspection light source wavelength of 13.5 nm are being used or proposedincreasingly frequently as defect inspection apparatuses of EUV masksand masters thereof in the form EUV mask blanks, substrates with amultilayer reflective film and substrates.

In addition, in the case of multilayer reflective films of substrateswith multilayer reflective films used in conventional EUV masks,attempts have been made to reduce concave defects present on thesubstrate by depositing according to, for example, the method describedin Patent Literature 1. However, no matter how many defects attributableto concave defects in a substrate are able to be reduced, due to thehigh detection sensitivity of the aforementioned highly sensitive defectdetection apparatuses, there is still the problem of the number ofdetected defects (number of detected defects=number of criticaldefects+number of pseudo defects) being excessively large when a defectinspection is carried out on the multilayer reflective film.

In addition, attempts to solve problems in terms of depositing theabsorber layer (absorber film) and problems with the reflectance of EUVlight or inspection light have employed a composition ratio like thatdescribed in Patent Literature 2, for example, for the absorber layer ofa reflective mask blank used in conventional EUV masks. With respect tosurface roughness of the surface of the absorber layer as well,smoothing is considered to be favorable from the viewpoint of preventingexacerbation of pattern dimensional accuracy. However, no matter howmany deposition problems of the absorber layer are able to be resolved,if a defect inspection is carried out on an absorber layer using ahighly sensitive defect inspection apparatus having high detectionsensitivity as previously described, the problem results in which anexcessive number of defects are detected.

Pseudo defects as mentioned here refer to surface irregularities thatare permitted to be present on a substrate surface, multilayerreflective film or absorber layer that do not affect pattern transfer,and end up being incorrectly assessed as defects upon inspection with ahighly sensitive defect inspection apparatus. If a large number of suchpseudo defects are detected in a defect inspection, critical defectsthat do have an effect on pattern transfer end up being concealed by thelarge number of pseudo defects, thereby preventing critical defects frombeing discovered. For example, with currently popular defect inspectionapparatuses having an inspection light source wavelength of 266 nm or193 nm, more than 50,000 defects end up being detected in a defectinspection region (measuring, for example, 132 mm×132 mm) of asubstrate, substrate with multilayer reflective film or reflective maskhaving a size of, for example, 152 mm×152 mm, thereby obstructinginspections for the presence or absence of critical defects. Overlookingcritical defects in a defect inspection results in defects in thesubsequent semiconductor device volume production process and leads tounnecessary labor and economic losses.

With the foregoing in view, an object of the present invention is toprovide a reflective mask blank that is able to facilitate discovery ofcontaminants or scratches and other critical defects by inhibitingdetection of pseudo defects attributable to surface roughness of asubstrate or film in a defect inspection using a highly sensitive defectinspection apparatus, a method of manufacturing the reflective maskblank, a reflective mask and a method of manufacturing a semiconductordevice that uses that reflective mask.

In addition, an object of the present invention is to provide areflective mask blank that enables critical defects to be reliablydetected since the number of detected defects, including pseudo defects,is reduced even when using highly sensitive defect inspectionapparatuses that use light of various wavelengths, and achievessmoothness required by reflective mask blanks in particular, whilesimultaneously reducing the number of detected defects, including pseudodefects; a method of manufacturing that reflective mask blank; areflective mask; and a method of manufacturing a semiconductor devicethat uses the reflective mask.

Means for Solving the Problems

As a result of conducting extensive studies to solve the aforementionedproblems, the inventors of the present invention found that therelationship between bearing area (%) and bearing depth (nm), obtainedby measuring with an atomic force microscope, and maximum height (Rmax),have an effect on the inspection light source wavelength of a highlysensitive defect inspection apparatus. Therefore, detection of pseudodefects in a defect inspection can be inhibited and critical defects canbe made more conspicuous by specifying and managing the relationshipbetween bearing area (%) and bearing depth (nm) as well as maximumheight (Rmax) of those roughness (irregularity) components on thesurface of a film (such as an absorber film) formed on a main surface ofa substrate that end up being incorrectly assessed as pseudo defects bya highly sensitive inspection apparatus.

In addition, although attempts have been made to reduce the surfaceroughness of reflective mask blanks in the past, there is no knowncorrelation whatsoever with the detection of pseudo defects by highlysensitive defect inspection apparatuses.

Therefore, the present invention has the configurations indicated belowin order to solve the aforementioned problems.

The present invention is a reflective mask blank characterized by thefollowing Configurations 1 to 6, a method of manufacturing a reflectivemask blank characterized by the following Configurations 7 to 16, areflective mask characterized by the following Configuration 17, and amethod of manufacturing a semiconductor device characterized by thefollowing Configuration 18.

(Configuration 1)

Configuration 1 of the present invention is a reflective mask blank,having: a mask blank multilayer film comprising a multilayer reflectivefilm, obtained by alternately laminating a high refractive index layerand a low refractive index layer, and an absorber film on a main surfaceof a mask blank substrate; wherein, in the relationship between bearingarea (%) and bearing depth (nm) as measured with an atomic forcemicroscope for a 1 μm×1 μm region of the surface of the reflective maskblank on which the mask blank multilayer film is formed, the surface ofthe reflective mask blank satisfies the relationship of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧60(%/nm) and maximum height (Rmax)≦4.5 nm,wherein BA_(H), is defined as a bearing area of 30%, BA₇₀ is defined asa bearing area of 70%, and BD₃₀ and BD₇₀ respectively is defined asbearing depths corresponding to a bearing area of 30% and bearing areaof 70%.

According to Configuration 1, as a result of making the relationshipbetween bearing area (%) and bearing depth (nm), obtained by measuring a1 μm×1 μm region on the surface of the reflective mask blank on whichthe mask blank multilayer film is formed with an atomic forcemicroscope, to be a prescribed relationship, and making maximum height(Rmax) to be within a prescribed range, the detection of pseudo defectsin a defect inspection using a highly sensitive defect inspectionapparatus can be inhibited and critical defects can be made moreconspicuous.

(Configuration 2)

The reflective mask blank described in Configuration 1, wherein the maskblank multilayer film further comprises a protective film arranged incontact with a surface of the multilayer reflective film on the oppositeside from the mask blank substrate.

According to Configuration 2, since damage to the surface of themultilayer reflective film can be inhibited when fabricating a transfermask (EUV mask) as a result of the reflective mask blank having aprotective film on the multilayer reflective film, reflectanceproperties with respect to EUV light can be further improved. Inaddition, in a reflective mask blank, since detection of pseudo defectsin a defect inspection of the surface of the protective film using ahighly sensitive defect inspection apparatus can be inhibited, criticaldefects can be made to be more conspicuous.

(Configuration 3)

Configuration 3 of the present invention is the reflective mask blankdescribed in Configuration 1 or Configuration 2, wherein the mask blankmultilayer film further comprises an etching mask film arranged incontact with the surface of the absorber film on the opposite side fromthe mask blank substrate.

According to Configuration 3, by using an etching mask film havingdifferent dry etching properties from those of the absorber film, ahighly precise transfer pattern can be formed when forming a transferpattern on the absorber film.

(Configuration 4)

Configuration 4 of the present invention is the reflective mask blankdescribed in any of Configurations 1 to 3, wherein the absorber filmcomprises tantalum and nitrogen, and the nitrogen content is 10 at % to50 at %.

According to Configuration 4, as a result of the absorber filmcomprising tantalum and nitrogen and the nitrogen content thereof being10 at % to 50 at %, the relationship between bearing area (%) andbearing depth (nm), obtained by measuring a 1 μm×1 μm region on thesurface of the reflective mask blank on which the mask blank multilayerfilm is formed with an atomic force microscope, is made to be aprescribed relationship, maximum height (Rmax) is within a prescribedrange, and pattern edge roughness when patterning the absorber film canbe reduced because enlargement of crystal grains composing the absorberfilm can be inhibited.

(Configuration 5)

Configuration 5 of the present invention is the reflective mask blankdescribed in any of Configurations 1 to 4, wherein the film thickness ofthe absorber film is not more than 60 nm.

According to Configuration 5, by making the film thickness of theabsorber film to be not more than 60 nm, in addition to being able toreduce shadowing effects, maximum height (Rmax) and the relationshipbetween bearing area (%) and bearing depth (nm) in a 1 μm×1 μm region ofthe surface of the absorber film can be made to have favorable values,and a reflective mask blank can be obtained that is able to inhibit thedetection of pseudo defects in a defect inspection using a highlysensitive defect inspection apparatus.

(Configuration 6)

Configuration 6 of the present invention is the reflective mask blankdescribed in any of Configurations 1 to 5, wherein the absorber film hasa phase shift function by which the phase difference between lightreflected from the surface of the absorber film and light reflected fromthe surface of the multilayer reflective film or protective film wherethe absorber film is not formed has a prescribed phase difference.

According to Configuration 6, as a result of the absorber film having afunction by which the phase difference between reflected light from thesurface of the absorber film and reflected light from the surface of themultilayer reflective film or protective film, where the absorber filmis not formed, has a prescribed phase difference; a master for areflective mask in the form of a reflective mask blank is obtained thatdemonstrates improved transfer resolution by EUV light. In addition,because the film thickness of the absorber film required to demonstratephase shift effects needed to obtain a desired transfer resolution canbe reduced in comparison with the prior art, a reflective mask blank isobtained that exhibits reduced shadowing effects.

(Configuration 7)

Configuration 7 of the present invention is a method of manufacturing areflective mask blank having a mask blank multilayer film, comprising amultilayer reflective film, obtained by alternately laminating a highrefractive index layer and a low refractive index layer, and an absorberfilm on a main surface of a mask blank substrate, comprising: formingthe multilayer reflective film on the main surface of the mask blanksubstrate, and forming the absorber film on the multilayer reflectivefilm; wherein, the flow rate of atmospheric gas is controlled so that,in the relationship between bearing area (%) and bearing depth (nm) asmeasured with an atomic force microscope for a 1 μm×1 μm region of thesurface of the reflective mask blank on which the mask blank multilayerfilm is formed, the surface of the reflective mask blank satisfies therelationship of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧60(%/nm) and maximum height(Rmax)≦4.5 nm, wherein BA₃₀ is defined as a bearing area of 30%, BA₇₀ isdefined as a bearing area of 70%, and BD₃₀ and BD₇₀ respectively isdefined as bearing depths corresponding to a bearing area of 30% andbearing area of 70%.

According to Configuration 7, as a result of making the relationshipbetween a bearing area (%) and bearing depth (nm), obtained by measuringa 1 μm×1 μm region on the surface of the reflective mask blank on whichthe mask blank multilayer film is formed with an atomic forcemicroscope, to be a prescribed relationship and making maximum height(Rmax) to be within a prescribed range, a reflective mask blank can befabricated that is capable of inhibiting the detection of pseudo defectsin a defect inspection using a highly sensitive defect inspectionapparatus and making critical defects more conspicuous.

(Configuration 8)

Configuration 8 of the present invention is the method of manufacturinga reflective mask blank described in Configuration 7, wherein, when themultilayer reflective film is formed, the multilayer reflective film isformed by ion beam sputtering by alternately irradiating a sputteringtarget of a high refractive index material and a sputtering target of alow refractive index material with an ion beam.

According to Configuration 8, as a result of forming a multilayerreflective film by a prescribed ion beam sputtering method in the stepfor forming a multilayer reflective film, a multilayer reflective filmcan be reliably obtained having favorable reflectance properties withrespect to EUV light.

(Configuration 9)

Configuration 9 of the present invention is the method of manufacturinga reflective mask blank described in Configuration 7 or Configuration 8,wherein, when the absorber film is formed, the absorber film is formedby reactive sputtering using a sputtering target of an absorber filmmaterial, and the absorber film contains a component contained in theatmospheric gas during reactive sputtering.

According to Configuration 9, an absorber film having a prescribedcomposition can be obtained by forming the absorber film by reactivesputtering in the step for forming the absorber film. As a result ofadjusting the flow rate of atmospheric gas when depositing by reactivesputtering, the flow rate can be adjusted so that the relationshipbetween a bearing area (%) and bearing depth (nm), obtained by measuringa 1 μm×1 μm region on the surface of the reflective mask blank on whichthe mask blank multilayer film is formed with an atomic forcemicroscope, has a prescribed relationship and maximum height (Rmax) iswithin a prescribed range.

(Configuration 10)

Configuration 10 of the present invention is the method of manufacturinga reflective mask blank described in Configuration 9, wherein theatmospheric gas is a mixed gas containing an inert gas and nitrogen gas.

According to Configuration 10, an absorber film that has a suitablecomposition can be obtained, since the nitrogen flow rate can beadjusted as a result of the atmospheric gas used during formation of theabsorber film by reactive sputtering being a mixed gas containing aninert gas and nitrogen. As a result thereof, an absorber film can bereliably obtained in which the relationship between bearing area (%) andbearing depth (nm) on the surface of a mask blank multilayer film has aprescribed relationship and maximum height (Rmax) is within a prescribedrange.

(Configuration 11)

Configuration 11 of the present invention is the method of manufacturinga reflective mask blank described in any of Configurations 7 to 10,wherein the absorber film is formed using a sputtering target of amaterial containing tantalum.

According to Configuration 11, as a result of forming the absorber filmusing a sputtering target of a material containing tantalum when formingthe absorber film by reactive sputtering, an absorber film can be formedthat contains tantalum and has suitable absorption. In addition, anabsorber film can be reliably obtained in which the relationship betweenbearing area (%) and bearing depth (nm) on the surface of a mask blankmultilayer film has a prescribed relationship and maximum height (Rmax)is within a prescribed range.

(Configuration 12)

Configuration 12 of the present invention is the method of manufacturinga reflective mask blank described in Configuration 7 or Configuration 8,wherein, when the absorber film is formed, the absorber film is formedby sputtering using a sputtering target of a material of the absorberfilm, and the material and film thickness of the absorber film areselected so that the maximum height (Rmax) is not more than 4.5 nm and,in a relationship between bearing area (%) and bearing depth (nm) asmeasured with an atomic force microscope for a 1 μm×1 μM region, thesurface of the reflective mask blank satisfies the relationship of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧60(%/nm) and maximum height (Rmax)≦4.5 nm,wherein BA₃₀ is defined as a bearing area of 30%, BA₇₀ is defined as abearing area of 70%, and BD₃₀ and BD₇₀ respectively refer to bearingdepths corresponding to a bearing area of 30% and bearing area of 70%.

According to Configuration 12, as a result of selecting the material andfilm thickness of the absorber film in the step for forming an absorberfilm, the maximum height (Rmax) and the relationship between bearingarea (%) and bearing depth (nm) of a 1 μm×1 μm region on the surface ofthe mask blank multilayer film containing an absorber film can beadjusted to be within prescribed ranges of values.

(Configuration 13)

Configuration 13 of the present invention is the method of manufacturinga reflective mask blank described in Configuration 12, wherein thematerial of the absorber film is a material that contains nitrogen, andthe film thickness of the absorber film is not more than 60 nm.

According to Configuration 13, as a result of the material of theabsorber film containing nitrogen and the film thickness of the absorberfilm being not more than 60 nm, in addition to being able to reduceshadowing effects, the maximum height (Rmax) and the relationshipbetween bearing area (%) and bearing depth (nm) of a 1 μm×1 μm region onthe surface of the absorber film can be made to have favorable values,and a reflective mask blank is obtained, the reflective mask blank beingcapable of inhibiting the detection of pseudo defects in a defectinspection using a highly sensitive defect inspection apparatus.

(Configuration 14)

Configuration 14 of the present invention is the method of manufacturinga reflective mask blank described in any of Configurations 7 to 13,further comprising forming a protective film arranged in contact withthe surface of the multilayer reflective film.

According to Configuration 14, because damage to the surface of themultilayer reflective film can be inhibited when fabricating a transfermask (EUV mask) as a result of performing an additional step for forminga protective film, reflectance properties with respect to EUV light canbe further improved. In addition, in the resulting reflective maskblank, detection of pseudo defects in a defect inspection of the surfaceof the protective film using a highly sensitive defect inspectionapparatus can be inhibited, and critical defects can be made to be moreconspicuous.

(Configuration 15)

Configuration 15 of the present invention is the method of manufacturinga reflective mask blank described in Configuration 14, wherein theprotective film is formed by ion beam sputtering by irradiating asputtering target of a protective film material with an ion beam.

According to Configuration 15, because smoothing of the surface of theprotective film is obtained by forming the protective film by ion beamsputtering using a sputtering target of a protective film material inthe step for forming the absorber film, the absorber film formed on theprotective film and the surface of an etching mask formed on theabsorber film can be smoothened, thereby making this preferable.

(Configuration 16)

Configuration 16 of the present invention is the method of manufacturinga reflective mask blank described in any of Configurations 7 to 15,further comprising forming an etching mask film arranged in contact withthe surface of the multilayer reflective film.

According to Configuration 16, by forming an etching mask film havingdifferent dry etching properties from those of the absorber film, ahighly precise transfer pattern can be formed when forming a transferpattern on the absorber film.

(Configuration 17)

Configuration 17 of the present invention is a reflective mask having anabsorber pattern on the multilayer reflective film, the absorber patternbeing obtained by patterning the absorber film of the reflective maskblank described in any of Configurations 1 to 6 or a reflective maskblank obtained according to the method of manufacturing a reflectivemask blank described in any of Configurations 7 to 16, on the multilayerreflective film.

According to the reflective mask of Configuration 17, detection ofpseudo defects in a defect inspection using a highly sensitive defectinspection apparatus can be reduced, and critical defects can be made tobe more conspicuous.

(Configuration 18)

Configuration 18 of the present invention is a method of manufacturing asemiconductor device, comprising: a step for forming a transfer patternon a transferred substrate (a substrate to be transferred) by carryingout a lithography process with an exposure apparatus using thereflective mask described in Configuration 17.

According to the method of manufacturing a semiconductor device ofConfiguration 18, because a reflective mask from which contaminants,scratches and other critical defects have been removed can be used in adefect inspection using a highly sensitive defect inspection apparatus,a circuit pattern or other transfer pattern transferred to a resist filmformed on a transferred substrate such as a semiconductor substrate isfree of defects, and a semiconductor device that has a fine and highlyprecise transfer pattern can be fabricated.

Effects of the Invention

According to the reflective mask blank and reflective mask of thepresent invention as described above, the discovery of contaminants,scratches or other critical defects can be facilitated by inhibitingdetection of pseudo defects attributable to surface roughness of asubstrate or film in a defect inspection using a highly sensitive defectinspection apparatus. In a reflective mask blank and reflective maskused in EUV lithography in particular, a multilayer reflective filmformed on a main surface of a substrate, which exhibits highreflectance, is obtained while inhibiting pseudo defects. In addition,the aforementioned reflective mask blank can be reliably fabricatedaccording to the method of manufacturing a reflective mask blank of thepresent invention as described.

In addition, according to the method of manufacturing a semiconductordevice as previously described, because a reflective mask from whichcontaminants, scratches and other critical defects have been removed canbe used in a defect inspection using a highly sensitive defectinspection apparatus, a circuit pattern or other transfer pattern formedon a transferred substrate such as a semiconductor substrate is free ofdefects, and a semiconductor device can be fabricated that has a fineand highly precise transfer pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a perspective view showing a mask blank substrate accordingto one embodiment of the present invention. FIG. 1(b) is across-sectional schematic diagram showing a mask blank substrate of thepresent embodiment.

FIG. 2 is a cross-sectional schematic diagram showing one example of theconfiguration of a substrate with a multilayer reflective film accordingto one embodiment of the present invention.

FIG. 3 is a cross-sectional schematic diagram showing one example of theconfiguration of a reflective mask blank according to one embodiment ofthe present invention.

FIG. 4 is a cross-sectional schematic diagram showing one example of areflective mask according to one embodiment of the present invention.

FIG. 5 is a cross-sectional schematic diagram showing another example ofthe configuration of a reflective mask blank according to one embodimentof the present invention.

FIG. 6 is a graph indicating the results of measuring bearing curves ofthe surface roughness of reflective mask blanks of Example 1 andComparative Example 1 of the present invention.

FIG. 7 is a graph indicating BA₇₀, BA₃₀, BD₇₀ and BD₃₀ in the bearingcurve measurement results of Example 1.

FIG. 8 is a graph indicating BA₇₀, BA₃₀, BD₇₀ and BD₃₀ in the bearingcurve measurement results of Comparative Example 1.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

The present invention is a reflective mask blank having a mask blankmultilayer film comprising a multilayer reflective film, obtained byalternately laminating a high refractive index layer and a lowrefractive index layer, and an absorber film on a main surface of a maskblank substrate.

FIG. 5 is a schematic diagram showing one example of a reflective maskblank 30 of the present invention. The reflective mask blank 30 of thepresent invention has a mask blank multilayer film 26 on a main surfaceof a mask blank substrate 10. In the present description, the mask blankmultilayer film 26 refers to a plurality of films, comprising amultilayer reflective film 21 and an absorber film 24, formed bylaminating on a main surface of the mask blank substrate 10. The maskblank multilayer film 26 can further comprise a protective film 22formed between the multilayer reflective film 21 and the absorber film24, and/or an etching mask film 25 formed on the surface of the absorberfilm 24. With the reflective mask blank 30 shown in FIG. 5, the maskblank multilayer film 26 on a main surface of the mask blank substrate10 has the multilayer reflective film 21, the protective film 22, theabsorber film 24 and the etching mask film 25. Furthermore, insubsequent explanations, with respect to the etching mask film 25, theetching mask film 25 is assumed to be stripped after having formed atransfer pattern on the absorber film 24. However, in the reflectivemask blank 30 in which the etching mask film 25 is not formed, alaminated structure having a plurality of layers is employed for theabsorber film 24, and the reflective mask blank 30 may be that in whichthe absorber film 24 has been given the function of an etching mask byusing materials having mutually different etching properties for thematerials composing the plurality of layers.

In the present description, “having a mask blank multilayer film 26 on amain surface of the mask blank substrate 10” refers to the case in whichthe mask blank multilayer film 26 is arranged in contact with thesurface of the mask blank substrate 10, as well as the case in whichanother film is present between the mask blank substrate 10 and the maskblank multilayer film 26. In addition, “a film A arranged in contactwith the surface of a film B” refers to film A and film B being arrangedso as to make direct contact without having another film interposedbetween film A and film B.

FIG. 3 is a schematic diagram showing another example of the reflectivemask blank 30 of the present invention. In the case of the reflectivemask blank 30 of FIG. 3, although the mask blank multilayer film 26 hasthe multilayer reflective film 21, the protective film 22 and theabsorber film 24, it does not have the etching mask film 25.

In the reflective mask blank 30 of the present invention, therelationship between bearing area (%) and bearing depth (nm), obtainedby measuring a 1 μm×1 μm region on the surface of the reflective maskblank 30, on which the mask blank multilayer film 26 is formed, with anatomic force microscope, has a prescribed relationship and the maximumheight (Rmax) of surface roughness is within a prescribed range.

According to the reflective mask blank 30 of the present invention, thediscovery of contaminants, scratches or other critical defects can befacilitated by inhibiting the detection of pseudo defects attributableto the surface roughness of a substrate or film during a defectinspection using a highly sensitive defect inspection apparatus.

Next, the following provides an explanation of the parameters of surfaceroughness (Rmax, Rms) and the relationship of a bearing curve (bearingarea (%) and bearing depth (nm)), which indicate the surface morphologyof a main surface of the reflective mask blank 30 on which the maskblank multilayer film 26 is formed.

First, Rms (root mean square), which is a typical indicator of surfaceroughness, refers to root mean square roughness and is the square rootof the value obtained by averaging the squares of the deviation from anaverage line to a measurement curve. Rms is represented by the followingformula (1):

$\begin{matrix}{\left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\mspace{610mu}} & \; \\{{Rms} = \sqrt{\frac{1}{l}{\int_{0}^{1}{{Z^{2}(x)}\ {\mathbb{d}x}}}}} & (1)\end{matrix}$

wherein, l represents a reference length and Z represents the heightfrom the average line to the measurement curve.

Similarly, Rmax, which is also a typical indicator of surface roughness,is the maximum height of surface roughness, and is the differencebetween the absolute values of maximum peak height and maximum troughdepth on a roughness curve.

Rms and Rmax have conventionally been used to manage the surfaceroughness of the mask blank substrate 10, and are superior with respectto enabling surface roughness to be ascertained in terms of numericalvalues. However, because Rms and Rmax both only consist of informationrelating to height, they do not contain information relating to subtlechanges in surface morphology.

In contrast, a bearing curve consists of a plot obtained by cuttingsurface irregularities in a measurement region on a main surface of thereflective mask blank 30 at an arbitrary height (horizontal plane) andplotting the percentages of the area of the cut sections versus the areaof the measurement region. A bearing curve makes it possible tovisualize and quantify variations in surface roughness of the reflectivemask blank 30.

A bearing curve is normally generated by plotting bearing area (%) onthe vertical axis and plotting bearing depth (nm) on the horizontalaxis. A bearing area of 0(%) indicates the highest point on thereflective mask blank measured, while a bearing area of 100(%) indicatesthe lowest point on the surface of the reflective mask blank measured.Thus, the difference between the depth at a bearing area of 0(%) and thedepth at a bearing area of 100(%) becomes the aforementioned maximumheight (Rmax) of surface roughness. Furthermore, although the term“bearing depth” is used in the present invention, this has the samemeaning as “bearing height”. In the case of “bearing height”, contraryto the above, a bearing area of 0(%) indicates the lowest point on thesurface of the reflective mask blank measured, while a bearing area of100(%) indicates the highest point on the surface of the reflective maskblank measured. The following provides an explanation of managing abearing curve in the reflective mask blank of the present embodiment.

In the reflective mask blank 30 of the present invention, in therelationship between bearing area (%) and bearing depth (nm), obtainedby measuring a 1 μm×1 μm region on the surface of the reflective maskblank 30 on which the mask blank multilayer film 26 is formed with anatomic force microscope, when a bearing area of 30% is defined as BA₃₀,a bearing area of 70% is defined as BA₇₀, and bearing depthscorresponding to a bearing area of 30% and bearing area of 70% aredefined as BD₃₀ and BD₇₀, respectively, the surface of the reflectivemask blank 30 satisfies the relationship of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧60(%/nm) and maximum height (Rmax) 4.5 nm.

Namely, the aforementioned (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) (units: %/nm)represents the slope of a bearing curve over a bearing area of 30% to70%, and as a result of making that slope to be not less than 60(%/nm),bearing area reaches 100% at a shallower bearing depth (nm). In otherwords, because surface irregularities (surface roughness) composing thesurface of the reflective mask blank 30 have an extremely uniformsurface morphology while maintaining extremely high smoothness,variations in surface irregularities (surface roughness) resulting inthe detection of pseudo defects in a defect inspection can be reduced,thereby making it possible to inhibit detection of pseudo defects in adefect inspection using a highly sensitive defect inspection apparatusand making critical defects more conspicuous.

In the present invention, the aforementioned 1 μm×1 μm region may be anarbitrary location of a transfer pattern formation region. If the sizeof the mask blank substrate 10 is that of a 6025 plate (152 mm×152mm×6.35 mm), then the transfer pattern formation region can be, forexample, a 142 mm×142 mm region, obtained by excluding the peripheralregion of the surface of the reflective mask blank substrate 30, a 132mm×132 mm region, a 132 mm×104 mm region, or the aforementionedarbitrary location can be a region located in the center of the surfaceof the reflective mask blank 30, for example.

In addition, in the present invention, the aforementioned 1 μm×1 μmregion can be a region located in the center of the film surface of themask blank multilayer film 26. For example, if the film surface of themask blank multilayer film 26 of the reflective mask blank 30 has arectangular shape, the aforementioned center is located at theintersection of the diagonal lines of the aforementioned rectangle.Namely, the aforementioned intersection and the center of theaforementioned region (and the center of the region is the same as thecenter of the film surface) coincide.

In addition, the previously explained 1 μm×1 μm region, the transferpattern formation region and the arbitrary location can also be appliedto the mask blank substrate 10 and a substrate with a multilayerreflective film 20 depending on the case.

From the viewpoint of inhibiting detection of pseudo defects, thesurface of the reflective mask blank 30 preferably has a surfacemorphology in which surface irregularities (surface roughness) composinga main surface are extremely uniform, and preferably(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧65(%/nm), more preferably(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧80(%/nm), even more preferably(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧95(%/nm), even more preferably(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧110(%/nm), even more preferably(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧125(%/nm), and still more preferably(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧150(%/nm). In addition, from a similarviewpoint, the surface roughness of the surface of the reflective maskblank 30 preferably also has high smoothness, and the maximum height(Rmax) of surface roughness is preferably not more than 4.25 nm, morepreferably not more than 4.0 nm, more preferably not more than 3.75 nm,more preferably not more than 3.5 nm, more preferably not more than 3.0nm, more preferably not more than 2.75 nm, and still more preferably notmore than 2.5 nm.

In addition, managing surface roughness of the surface of the reflectivemask blank 30 using root mean square roughness (Rms) in addition to theaforementioned maximum height (Rmax) is preferable from the viewpoint ofimproving reflectance and other optical properties of the multilayerreflective film 21, protective film 22 and absorber film 24 formed onthe surface of the reflective mask blank 30, for example. The surfaceroughness of the surface of the reflective mask blank 30 is such thatthe root mean square roughness (Rms) is preferably not more than 0.5 nm,more preferably not more than 0.45 nm, more preferably not more than 0.4nm, more preferably not more than 0.3 nm and still more preferably notmore than 0.25 nm.

In addition, the surface of the reflective mask blank 30 preferably hasa surface morphology such that, in a frequency distribution obtained byplotting the relationship between bearing depth, obtained by measuringwith an atomic force microscope, and the frequency (%) of the resultingbearing depth, the absolute value of the bearing depth corresponding tothe center of an approximated curve determined from the aforementionedplotted points, or the half width determined from the maximum frequencyof the aforementioned plotted points, is smaller than the absolute valueof the bearing depth corresponding to one-half (½) the maximum height(Rmax) of surface roughness of the surface of the aforementionedreflective mask blank. This surface morphology is such that theproportion of surface irregularities that compose the surface of thereflective mask blank 30 that consists of concave portions is greaterthan the proportion that consists of convex portions with respect to areference surface. Thus, when laminating a plurality of thin films onthe surface of the reflective mask blank 30, because the size of defectson the aforementioned main surface tends to become small, this ispreferable in terms of defect quality. This effect is especiallydemonstrated when forming the multilayer reflective film 21 to besubsequently described on the aforementioned main surface in particular.Moreover, on the surface of the absorber film 24 of the etching maskfilm 25, adhesiveness with a resist film coated thereon is thought to befurther improved.

According to the reflective mask blank of the present invention, thedetection of pseudo defects attributable to the surface roughness of asubstrate or film in a defect inspection using a highly sensitive defectinspection apparatus can be inhibited, and the discovery of contaminantsor scratches and other critical defects can be facilitated.

Next, a detailed explanation is provided of the reflective mask blank 30of the present invention.

[Mask Blank Substrate 10]

First, the mask blank substrate 10 that can be used to fabricate thereflective mask blank 30 of the present invention will be described.

FIG. 1(a) is a perspective view showing an example of the mask blanksubstrate 10 that can be used to fabricate the reflective mask blank 30of the present invention. FIG. 1(b) is a cross-sectional schematicdiagram of the mask blank substrate 10 shown in FIG. 1(a).

The mask blank substrate 10 (which may be simply referred to as thesubstrate 10) is a rectangular plate-like body, and has two opposingmain surfaces 2 and an edge face 1. The two opposing main surfaces 2constitute an upper surface and a lower surface of this plate-like body,and are formed so as to be mutually opposing. In addition, at least oneof the two opposing main surfaces 2 is a main surface on which atransfer pattern is to be formed.

The edge face 1 constitutes the lateral surface of this plate-like body,and is adjacent to the outer edges of the opposing main surfaces 2. Theedge face 1 has a flat edge face portion 1 d and a curved edge faceportion 1 f. The flat edge face portion 1 d is a surface that connects aside of one of the opposing main surfaces 2 and a side of the otheropposing main surface 2, and comprises a lateral surface portion 1 a anda chamfered surface portion 1 b. The lateral surface portion 1 a is aportion (T surface) that is nearly perpendicular to the opposing mainsurfaces 2 in the flat edge face portion 1 d. The chamfered surfaceportion 1 b is a portion (C surface) that is chamfered between thelateral surface portion 1 a and the opposing main surfaces 2, and isformed between the lateral surface portion 1 a and the opposing mainsurfaces 2.

The curved edge face portion 1 f is a portion (R portion) that isadjacent to the vicinity of a corner portion 10 a of the substrate 10when the substrate 10 is viewed from overhead, and comprises a lateralsurface portion 1 c and a chamfered surface portion 1 e. Here, when thesubstrate 10 is viewed from overhead, the substrate 10 appears in, forexample, a direction perpendicular to the opposing main surfaces 2. Inaddition, the corner portion 10 a of the substrate 10 refers to, forexample, the vicinity of the intersection of two sides along the outeredge of the opposing main surfaces 2. An intersection of two sides isthe intersection of lines respectively extending from two sides. In thepresent example, the curved end face portion 1 f is formed into a curvedshape by rounding the corner portion 10 a of the substrate 10.

In order to more reliably achieve the object of the present invention,the main surfaces of the mask blank substrate 10 used in the reflectivemask blank 30 of the present invention and the surface of the multilayerreflective film 21 of the substrate with a multilayer reflective film 20preferably have the aforementioned prescribed relationship betweenbearing area (%) and bearing depth (nm) as well as a prescribed range ofmaximum height (Rmax) in the same manner as the surface of thereflective mask blank 30 of the present invention.

In addition, the main surfaces of the mask blank substrate 10 arepreferably processed by catalyst referred etching. Catalyst referredetching (CARE) refers to a surface processing method involving arranginga processing target (mask blank substrate 10) and catalyst in atreatment liquid or supplying a treatment liquid between the processingtarget and the catalyst, allowing the processing target and catalyst tomake contact, and processing the processing target with an activespecies generated from molecules in the treatment liquid that have beenadsorbed on the catalyst at that time. Furthermore, when the processingtarget is composed of a solid oxide such as glass, water is used for thetreatment liquid, the processing target is allowed to contact thecatalyst in the presence of the water, and the catalyst and surface ofthe processing target are allowed to undergo relative motion and thelike to remove decomposition products of hydrolysis from the surface ofthe processing target.

Main surfaces of the mask blank substrate 10 are selectively processedby catalyst referred etching starting from convex portions that contacta reference surface in the form of a catalyst surface. Consequently,surface irregularities (surface roughness) that compose the mainsurfaces retain an extremely high level of smoothness resulting in anextremely uniform surface morphology, while also resulting in a surfacemorphology in which the proportion of concave portions that compose thereference surface is greater than the proportion of convex portions.Thus, when laminating a plurality of thin films on the aforementionedmain surfaces, since the size of defects on the main surfaces tends tobecome small, surface processing by catalyst referred etching ispreferable in terms of defect quality. This effect is especiallydemonstrated when forming the multilayer reflective film 21 to besubsequently described on the aforementioned main surfaces inparticular. In addition, as a result of processing the main surfaces bycatalyst referred etching as previously described, a surface having theaforementioned prescribed relationship between bearing area (%) andbearing depth (nm) and a prescribed range of maximum height (Rmax) canbe formed comparatively easily.

Furthermore, when the material of the substrate 10 is a glass material,at least one type of material selected from the group consisting ofplatinum, gold, transition metals and alloys comprising at least one ofthese materials can be used as the catalyst. In addition, at least onetype of treatment liquid selected from the group consisting of purewater, functional water such as ozonated water or hydrogen water,low-concentration aqueous alkaline solutions and low-concentrationaqueous acidic solutions can be used for the treatment liquid.

As a result of making the relationship between bearing area (%) andbearing depth (nm) and maximum height (Rmax) of the main surfaces to bewithin the aforementioned ranges as previously described, detection ofpseudo defects can be significantly inhibited in a defect inspection by,for example, the “MAGICS M7360” Mask/Substrate/Blank Defect InspectionApparatus for EUV Exposure manufactured by Lasertec Corp. (inspectionlight source wavelength: 266 nm) or the “Teron 610” Reticule, OpticalMask/Blank and UV Mask/Blank Defect Inspection Apparatuses manufacturedby KLA-Tencor Corp. (inspection light source wavelength: 193 nm).

Furthermore, the aforementioned inspection light source wavelength isnot limited to 266 nm and 193 nm. A wavelength of 532 nm, 488 nm, 364 nmor 257 nm may also be used for the inspection light source wavelength.

A main surface on the side, on which a transfer pattern of the maskblank substrate 10 used in the reflective mask blank 30 of the presentinvention is formed, is preferably processed so as to have high flatnessat least from the viewpoints of obtaining pattern transfer accuracy andpositional accuracy. In the case of an EUV reflective mask blanksubstrate, flatness in a 132 mm×132 mm region or a 142 mm×142 mm regionon a main surface of the substrate 10 on the side on which a transferpattern is formed is preferably not more than 0.1 μm and particularlypreferably not more than 0.05 μm. In addition, flatness in a 132 mm×132mm region on a main surface of the substrate 10 on which a transferpattern is formed is more preferably not more than 0.03 μm. In addition,the main surface on the opposite side from the side on which a transferpattern is formed is the side that is clamped with an electrostaticchuck when the substrate is placed in an exposure apparatus, andflatness in a 142 mm×142 mm region is preferably not more than 1 μm andparticularly preferably not more than 0.5 μm.

Any material may be used for the material of the reflective mask blanksubstrate 10 for EUV exposure provided it has low thermal expansionproperties. For example, a SiO₂—TiO₂-based glass having low thermalexpansion properties (such as a two-element system (SiO₂—TiO₂) orthree-element system (such as SiO₂—TiO₂—SnO₂)), or a so-calledmulticomponent glass such as SiO₂—Al₂O₃—Li₂O-based crystallized glass,can be used. In addition, a substrate other than the aforementionedglass made of silicon or metal and the like can also be used. An exampleof the aforementioned metal substrate is an invar alloy (Fe—Ni-basedalloy).

As was previously described, in the case of the mask blank substrate 10for EUV exposure, a multicomponent glass material is used since thesubstrate is required to have low thermal expansion properties. However,there is the problem of it being difficult to obtain high smoothnesswith a multicomponent glass material in comparison with synthetic quartzglass. In order to solve this problem, a thin film composed of a metalor an alloy, or a thin film composed of a material containing at leastone of oxygen, nitrogen and carbon in a metal or alloy, is formed on asubstrate composed of a multicomponent glass material. A surface havingthe aforementioned prescribed relationship between bearing area (%) andbearing depth (nm) and a prescribed range of maximum height (Rmax) canthen be formed comparatively easily by subjecting the surface of thethin film to mirror polishing and surface treatment.

Preferable examples of the material of the aforementioned thin filminclude Ta (tantalum), alloys containing Ta and Ta compounds containingat least one of oxygen, nitrogen and carbon in Ta or an alloy containingTa. Examples of Ta compounds that can be applied include those selectedfrom TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO,TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON and TaSiCON. Amongthese Ta compounds, TaN, TaON, TaCON, TaBN, TaBON, TaBCON, TaHfN,TaHfON, TaHfCON, TaSiN, TaSiON and TaSiCON that contain nitrogen (N) areused more preferably. Furthermore, from the viewpoint of high smoothnessof the thin film surface, the aforementioned thin film preferably has anamorphous structure. The crystal structure of the thin film can bemeasured with an X-ray diffraction (XRD) analyzer.

Furthermore, in the present invention, there are no particularlimitations on the processing method used to obtain the aforementionedprescribed relationship between bearing area (%) and bearing depth (nm)and the prescribe range of maximum height (Rmax). The present inventionis characterized in the managing of the relationship between bearingarea (%) and bearing depth (nm) along with maximum height (Rmax) on thesurface of the reflective mask blank 30, and can be realized by, forexample, processing methods like those exemplified in the examples to bedescribed below.

[Substrate with Multilayer Reflective Film 20]

The following provides an explanation of the substrate with a multilayerreflective film 20 that can be used in the reflective mask blank 30 ofthe present invention.

FIG. 2 is a schematic diagram of one example of the substrate with amultilayer reflective film 20 able to be used in the reflective maskblank 30.

The substrate with a multilayer reflective film 20 of the presentembodiment has a structure having the multilayer reflective film 21 on amain surface of the previously explained mask blank substrate 10 on theside on which a transfer pattern is formed. This multilayer reflectivefilm 21 imparts a function of reflecting EUV light in a reflective mask40 for EUV lithography, and adopts a configuration in which elementshaving different refractive indices are cyclically laminated.

There are no particular limitations on the material of the multilayerreflective film 21 provided it reflects EUV light. The reflectance ofthe multilayer reflective film 21 alone is normally not less than 65%and the upper limit thereof is normally 73%. This type of multilayerreflective film 21 can be that of a multilayer reflective film 21 inwhich a thin film composed of a high refractive index material (highrefractive index layer) and a thin film composed of a low refractiveindex material (low refractive index layer) are alternately laminatedfor about 40 to 60 cycles.

For example, the multilayer reflective film 21 for EUV light of awavelength of 13 nm to 14 nm preferably consists of an Mo/Si cyclicallylaminated film obtained by alternately laminating about 40 cycles of anMo film and Si film. In addition, a multilayer reflective film used inthe region of EUV light can consist of, for example, an Ru/Si cyclicallylaminated film, Mo/Be cyclically laminated film, Mo compound/Si compoundcyclically laminated film, Si/Nb cyclically laminated film, Si/Mo/Rucyclically laminated film, Si/Mo/Ru/Mo cyclically laminated film orSi/Ru/Mo/Ru cyclically laminated film.

The method used to form the multilayer reflective film 21 is known inthe art. The multilayer reflective film 21 can be formed by depositingeach layer by, for example, magnetron sputtering or ion beam sputtering.In the case of the aforementioned Mo/Si cyclically laminated film, an Sifilm having a thickness of about several nm is first deposited on thesubstrate 10 using an Si target by, for example, ion beam sputtering,followed by depositing an Mo film having a thickness of about several nmusing an Mo target and, with this deposition comprising one cycle,laminating for 40 to 60 cycles, to form the multilayer reflective film21.

When fabricating the reflective mask blank 30 of the present invention,the multilayer reflective film 21 is preferably formed by ion beamsputtering by alternately irradiating a sputtering target of a highrefractive index material and a sputtering target of a low refractiveindex material. As a result of forming the multilayer reflective film bya prescribed ion beam sputtering method, the multilayer reflective film21 having favorable reflectance properties with respect to EUV light canbe reliably obtained.

In the reflective mask blank 30 of the present invention, the mask blankmultilayer film 26 preferably further comprises the protective film 22arranged in contact with the surface of the multilayer reflective film21 on the opposite side from the mask blank substrate 10.

The protective film 22 (see FIG. 3) can be formed to protect themultilayer reflective film 21 from dry etching or wet cleaning in themanufacturing process of the reflective mask 40 for EUV lithography. Inthis manner, an aspect having the multilayer reflective film 21 and theprotective film 22 on the mask blank substrate 10 can also constitutethe substrate with a multilayer reflective film 20 in the presentinvention.

Furthermore, materials selected from, for example, Ru, Ru—(Nb, Zr, Y, B,Ti, La, Mo), Si—(Ru, Rh, Cr, B), Si, Zr, Nb, La and B can be used forthe material of the aforementioned protective film 22. Among thesematerials, reflectance properties of the multilayer reflective film 21can be made more favorable if a material comprising ruthenium (Ru) isapplied. More specifically, the material of the protective film 22 ispreferably Ru or Ru—(Nb, Zr, Y, B, Ti, La, Mo). This type of protectivefilm 22 is particularly effective in the case of patterning the absorberfilm 24 using a Ta-based material for the absorber film and dry etchingusing a Cl-based gas.

Furthermore, in the substrate with a multilayer reflective film 20, thesurface of the multilayer reflective film 21 or the protective film 22is preferably such that the relationship between bearing area (%) andbearing depth (nm), obtained by measuring a 1 μm×1 μm region with anatomic force microscope, when a bearing area of 30% is defined as BA₃₀,a bearing area of 70% is defined as BA₇₀, and bearing depthscorresponding to a bearing area of 30% and bearing area of 70% aredefined as BD₃₀ and BD₇₀, respectively, satisfies the relationship of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧230(%/nm) and the maximum height of surfaceroughness (Rmax)≦4.5 nm. As a result of employing this configuration,when carrying out a defect inspection on the substrate with a multilayerreflective film 20 with a highly sensitive defect inspection apparatususing the aforementioned inspection light source wavelength, detectionof pseudo defects can be inhibited considerably. In addition, there isalso the effect of high reflectance because the smoothness of thesurface of the multilayer reflective film 21 or the protective film 22is improved and surface roughness (Rmax) can be decreased.

The surface of the multilayer reflective film 21 or the protective film22 is preferably such that (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧250(%/nm), morepreferably such that (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧300(%/nm), even morepreferably such that (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧350(%/nm), even morepreferably such that (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧400(%/nm), even morepreferably such that (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧450(%/nm) and still morepreferably such that (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧500(%/nm). In addition,from the same viewpoint, the surface roughness of the multilayerreflective film 21 or the protective film 22 is preferably such that themaximum height (Rmax) of surface roughness is preferably such that(Rmax)≦1.3 nm, more preferably such that (Rmax)≦1.2 nm, even morepreferably such that (Rmax)≦1.1 nm and still more preferably such that(Rmax)≦1.0 nm.

In order to maintain the aforementioned range of the surface morphologyof the substrate 10 and enable the surface of the multilayer reflectivefilm 21 or the protective film 22 to have a relationship between bearingarea (%) and bearing depth (nm) as well as surface roughness maximumheight (Rmax) within the aforementioned ranges, the multilayerreflective film 21 is obtained by depositing by sputtering so that ahigh refractive index layer and a low refractive index layer accumulateon an angle to the normal of a main surface of the substrate 10. Morespecifically, the incident angle of sputtered particles for depositing alow refractive index layer consisting of Mo and the like and theincident angle of sputtered particles for depositing a high refractiveindex layer consisting of Si and the like are greater than 0 degrees tonot more than 45 degrees, more preferably greater than 0 degrees to notmore than 40 degrees, and even more preferably greater than 0 degrees tonot more than 30 degrees. Moreover, the protective film 22 formed on themultilayer reflective film 21 is also preferably formed by ion beamsputtering in continuation therefrom so that the protective film 22accumulates on an angle to the normal of a main surface of the substrate10.

In addition, in the substrate with a multilayer reflective film 20, aback side electrically conductive film 23 (see FIG. 3) for the purposeof electrostatic clamping can also be formed on the surface of the maskblank substrate 10 on the opposite side from the surface contacting themultilayer reflective film 21 of the substrate 10. In this manner, anaspect having the multilayer reflective film 21 and the protective film22 on the side of the mask blank substrate 10 on which a transferpattern is formed, and having the back side electrically conductive film23 on the surface on the opposite side from the surface contacting themultilayer reflective film 21, also constitutes the substrate with amultilayer reflective film 20 in the present invention. Furthermore, theelectrical property (sheet resistance) required by the back sideelectrically conductive film 23 is normally not more than 100 Ω/square.The method used to form the back side electrically conductive film 23 isa known method, and it can be formed, for example, using a metal oralloy target of Cr or Ta and the like by magnetron sputtering or ionbeam sputtering.

In addition, the substrate with a multilayer reflective film 20 of thepresent embodiment may also have a base layer formed between the maskblank substrate 10 and the multilayer reflective film 21. The base layercan be formed for the purpose of improving smoothness of a main surfaceof the substrate 10, reducing defects, demonstrating the effect ofenhancing reflectance of the multilayer reflective film 21, andcompensating for stress in the multilayer reflective film 21.

[Reflective Mask Blank 30]

The following provides an explanation of the reflective mask blank 30 ofthe present invention.

FIG. 3 is a schematic diagram showing one example of the reflective maskblank 30 of the present invention.

The reflective mask blank 30 of the present invention employs aconfiguration in which an absorber film 24 serving as a transfer patternis formed on the protective film 22 of the substrate with a multilayerreflective film 20 that is previously explained.

The aforementioned absorber film 24 is only required to be that whichhas a function that absorbs exposure light in the form of EUV light, andhas a desired difference in reflectance between light reflected by theaforementioned multilayer reflective film 21 and the protective film 22and light reflected by an absorber pattern 27.

For example, reflectance with respect to EUV light of the absorber film24 is set to between 0.1% and 40%. Moreover, in addition to theaforementioned difference in reflectance, the absorber film 24 may alsohave a desired phase difference between light reflected by theaforementioned multilayer reflective film 21 or the protective film 22and light reflected by the absorber pattern 27. Furthermore, in the caseof having such a phase difference between reflected light, the absorberfilm 24 in the reflective mask blank 30 may be referred to as a phaseshift film. In the case of improving the contrast of reflected light ofa reflective mask obtained by providing the aforementioned desired phasedifference between reflected light, the phase difference is preferablyset to within the range of 80 degrees±10 degrees, the reflectance of theabsorber film 24 in terms of absolute reflectance is preferably set to1.5% to 30%, and the reflectance of the absorber film 24 with respect tothe surface of the multilayer reflective film 21 and/or the protectivefilm 22 is preferably set to 2% to 40%.

The aforementioned absorber film 24 may be a single layer or amultilayered structure. In the case of a multilayered structure, thelaminated films may be of the same material or different materials. Thematerials and composition of the laminated film may vary incrementallyand/or continuously in the direction of film thickness.

There are no particular limitations on the material of theaforementioned absorber film 24. For example, a material having thefunction of absorbing EUV light that is composed of Ta (tantalum) aloneor a material having Ta as the main component thereof is usedpreferably. A material having Ta as the main component thereof isnormally a Ta alloy. The crystalline state of this absorber film 24 issuch that it preferably has an amorphous or microcrystalline structurefrom the viewpoints of smoothness and flatness. Examples of materialsthat can be used for the material having Ta as the main componentthereof include materials selected from materials containing Ta and B,materials containing Ta and N, materials containing Ta and B and furthercontaining at least O or N, materials containing Ta and Si, materialscontaining Ta, Si and N, materials containing Ta and Ge, and materialscontaining Ta, Ge and N. In addition, an amorphous structure is easilyobtained by adding, for example, B, Si or Ge and the like to Ta, therebymaking it possible to improve smoothness. Moreover, if N and/or O areadded to Ta, resistance to oxidation improves, thereby making itpossible to improve stability over time. In order to maintain thesurface morphology of the substrate 10 and the substrate with amultilayer reflective film 20 within the aforementioned ranges and allowthe surface of the absorber film 24 to have the relationship betweensurface area (%) and surface depth (nm) as well as the surface roughnessmaximum height (Rmax) within the aforementioned ranges, amicrocrystalline structure or amorphous structure is preferably employedfor the absorber film 24. The crystal structure can be confirmed with anX-ray diffraction (XRD) instrument.

More specifically, examples of materials containing tantalum that formthe absorber film 24 include tantalum metal and materials that containtantalum and one or more elements selected from nitrogen, oxygen, boronand carbon, but do not substantially contain hydrogen. Examples thereofinclude Ta, TaN, TaON, TaBN, TaBON, TaCN, TaBON, TaBCN and TaBOCN. Theaforementioned materials may also contain metals other than tantalumwithin a range that allows the effects of the present invention to beobtained. When the material containing tantalum that forms the absorberfilm 24 contains boron, it facilitates to control the absorber film 24so as to adopt an amorphous (non-crystalline) structure.

The absorber film 24 of the mask blank is preferably formed with amaterial containing tantalum and nitrogen. The nitrogen content in theabsorber film 24 is preferably not more than 50 at %, more preferablynot more than 30 at %, even more preferably not more than 25 at % andstill more preferably not more than 20 at %. The nitrogen content in theabsorber film 24 is preferably not less than 5 at %.

In the reflective mask blank 30 of the present invention, the absorberfilm 24 preferably contains tantalum and nitrogen and the nitrogencontent is 10 at % to 50 at %, more preferably 15 at % to 50 at %, andeven more preferably 30 at % to 50 at %. As a result of the absorberfilm 24 containing tantalum and nitrogen and the nitrogen content being10 at % to 50 at %, the aforementioned prescribed relationship betweenbearing area (%) and bearing depth (nm) as well as the aforementionedprescribed range of maximum height (Rmax) can be obtained on the surfaceof the absorber film 24, and because enlargement of crystal grains thatcompose the absorber film 24 can be inhibited, the pattern edgeroughness when patterning the absorber film 24 can be reduced.

In the reflective mask blank 30 of the present invention, the filmthickness of the absorber film 24 is set to the film thickness requiredfor the absorber film 24 to have a desired difference in reflectancebetween light reflected by the multilayer reflective film 21 and theprotective film 22 and light reflected by the absorber pattern 27. Thefilm thickness of the absorber film 24 is preferably not more than 60 nmin order to reduce shadowing effects. As a result of making the filmthickness of the absorber film 24 to be not more than 60 nm, the maximumheight (Rmax) of the surface of the absorber film 24 can be furtherreduced, and the value of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) in the relationshipbetween bearing area (%) and bearing depth (nm) obtained by measuring a1 μm×1 μm region can be made even larger, thereby making it possible toinhibit the detection of pseudo defects in a defect inspection using ahighly sensitive defect inspection apparatus.

In addition, in the reflective mask blank 30 of the present invention,the aforementioned absorber film 24 can be given a phase shift functionhaving a desired phase shift difference between light reflected by theaforementioned multilayer reflective film 21 and the protective film 22and light reflected by the absorber pattern 27. In that case, areflective mask blank that serves as a master for a reflective maskhaving improved transfer resolution by EUV light, is obtained. Inaddition, because the film thickness of the absorber required todemonstrate a phase shift effect needed to obtain a desired transferresolution can be reduced in comparison with that of the prior art, areflective mask blank is obtained in which shadowing effects arereduced.

There are no particular limitations on the material of the absorber film24 having a phase shift function. For example, Ta alone or a materialhaving Ta as the main component thereof can be used as previouslydescribed, or another material may be used. Examples of materials otherthan Ta include Ti, Cr, Nb, Mo, Ru, Rh and W. In addition, an alloycontaining two or more elements among Ta, Ti, Cr, Nb, Mo, Ru, Rh and Wcan be used for the material, and a multilayer film can be usedconsisting of layers having these elements as materials thereof. Inaddition, one or more elements selected from nitrogen, oxygen and carbonmay also be contained in these materials. Among these, by employing amaterial that contains nitrogen, the maximum height (Rmax) of thesurface of the absorber film can be further reduced and the value of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) in the relationship between bearing area (%) andbearing depth (nm) obtained by measuring a 1 μm×1 μm region can be madeeven larger, and a reflective mask blank that is able to inhibit thedetection of pseudo defects in a defect inspection using a highlysensitive defect inspection apparatus can be obtained, thereby makingthis preferable. Furthermore, when using the absorber film 24 in theform of a laminated film, the laminated film may be a laminated filmconsisting of layers of the same material or a laminated film consistingof layers of different materials. When using a laminated film consistingof layers of different materials for the absorber film 24, the materialsthat compose this plurality of layers may be materials having mutuallydifferent etching properties to obtain an absorber film 24 having anetching mask function.

If the uppermost surface of the reflective mask blank 30 of the presentinvention is the absorber film 24, the relationship between bearing area(%) and bearing depth (nm), obtained by a measuring a 1 μm×1 μm regionon the surface of the absorber film 24 with an atomic force microscope,is made to have a prescribed relationship, and the surface roughnessmaximum height (Rmax) is made to be within a prescribed range. Accordingto the reflective mask blank 30 of the present invention having such aconfiguration, the detection of pseudo defects attributable to surfaceroughness of a substrate or film in a defect inspection using a highlysensitive defect inspection apparatus can be inhibited, and thediscovery of contaminants or scratches and other critical defects can befacilitated.

Furthermore, the reflective mask blank 30 of the present invention isnot limited to the configuration shown in FIG. 3. For example, a resistfilm serving as a mask for patterning the aforementioned absorber film24 can also be formed on the absorber film 24, and this reflective maskwith a resist film 30 can also constitute the reflective mask blank 30of the present invention. Furthermore, the resist film formed on theabsorber film 24 may be a positive resist or negative resist. Inaddition, the resist film may also be for electron beam drawing or laserdrawing. Moreover, a so-called hard mask (etching mask) film can also beformed between the absorber film 24 and the aforementioned resist film,and this aspect can also constitute the reflective mask blank 30 of thepresent invention.

In the reflective mask blank 30 of the present invention, the mask blankmultilayer film 26 preferably further comprises the etching mask film 25arranged in contact with the surface of the absorber film 24 on theopposite side form the mask blank substrate 10. If the reflective maskblank 30 shown in FIG. 5, the mask blank multilayer film 26 on a mainsurface of the mask blank substrate 10 further has the etching mask film25 in addition to the multilayer reflective film 21, the protective film22 and the absorber film 24. The reflective mask blank 30 of the presentinvention may further have a resist film on the uppermost surface of themask blank multilayer film 26 of the reflective mask blank 30 shown inFIG. 5.

More specifically, in the reflective mask blank 30 of the presentinvention, when the material of the absorber film 24 uses Ta alone or amaterial having Ta has the main component thereof, a structure ispreferably employed in which the etching mask film 25 composed of amaterial containing chromium is formed on the absorber film 24. As aresult of employing the reflective mask blank 30 having such astructure, the reflective mask 40 can be fabricated in which opticalproperties of the absorber film 24 with pattern are favorable even ifthe etching mask film 25 is removed by dry etching using a mixed gas ofa chlorine-based gas and oxygen gas after forming a transfer pattern onthe absorber film 24. In addition, a reflective mask 40 can befabricated in which line edge roughness of a transfer pattern formed onthe absorber film 24 is favorable.

Examples of materials containing chromium that form the etching maskfilm 25 include materials containing chromium and one or more elementsselected from nitrogen, oxygen, carbon and boron. Examples thereofinclude CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN and CrBOCN. Theaforementioned materials may also contain materials other than chromiumwithin a range that allows the effects of the present invention to beobtained. The film thickness of the etching mask film 25 is preferablynot less than 3 nm from the viewpoints of functioning as an etching maskwith which a transfer pattern is accurately formed on the absorber film24. In addition, the film thickness of the etching mask film 25 ispreferably not more than 15 nm from the viewpoint of reducing filmthickness of the resist film.

If the uppermost surface of the reflective mask blank 30 of the presentinvention is the etching mask blank 25, similar to the case of theuppermost surface of the reflective mask blank 30 being the absorberfilm 24, the relationship between bearing area (%) and bearing depth(nm), obtained by a measuring a 1 μm×1 μm region on the surface of theetching mask film 25 with an atomic force microscope, is made to have aprescribed relationship and surface roughness maximum height (Rmax) ismade to be within a prescribed range. According to the reflective maskblank 30 of the present invention having such a configuration, thedetection of pseudo defects attributable to surface roughness of asubstrate or film in a defect inspection using a highly sensitive defectinspection apparatus can be inhibited, and the discovery of contaminantsor scratches and other critical defects can be facilitated.

The following provides an explanation of a method of manufacturing thereflective mask blank 30 of the present invention.

The present invention is a method of manufacturing the reflective maskblank 30 having the mask blank multilayer film 26, comprising themultilayer reflective film 21, obtained by alternately laminating a highrefractive index layer and a low refractive index layer, and theabsorber film 24, on a main surface of the mask blank substrate 10. Themethod of manufacturing the reflective mask blank 30 of the presentinvention comprises a step for forming the multilayer reflective film 21on a main surface of the mask blank substrate 10, and a step for formingthe absorber film 24 on the multilayer reflective film 21. In the methodof manufacturing the reflective mask blank 30 of the present invention,the absorber film 24 is formed so that the surface of the reflectivemask blank 30 is such that, in the relationship between bearing area (%)and bearing depth (nm), obtained by measuring a 1 μm×1 μm region on thesurface thereof with an atomic force microscope, when a bearing area of30% is defined as BA₃₀, a bearing area of 70% is defined as BA₇₀, andbearing depths corresponding to a bearing area of 30% and bearing areaof 70% are defined as BD₃₀ and BD₇₀, respectively, the surface of thereflective mask blank 30 satisfies the relationship of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧60(%/nm) and the surface roughness maximumheight (Rmax)≦4.5 nm.

By making (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) to be not less than 60(%/nm)(preferably not less than 65(%/nm), more preferably not less than80(%/nm), even more preferably not less than 95(%/nm), even morepreferably not less than 110(%/nm), even more preferably not less than125(%/nm) and still more preferably not less than 150(%/nm)), and makingsurface roughness maximum value (Rmax) to not be more than 4.5 nm(preferably not more than 4.25 nm, more preferably not more than 4.0 nm,more preferably not more than 3.75 nm, more preferably not more than 3.5nm, more preferably not more than 3.0 nm, more preferably not more than2.75 nm, and still more preferably not more than 2.5 nm) on the surfaceof the reflective mask blank 30 of the present invention, the reflectivemask blank 30 can be fabricated in which the detection of pseudo defectsin a defect inspection using a highly sensitive defect inspectionapparatus can be inhibited and critical defects can be made moreconspicuous.

In the method of manufacturing the reflective mask blank 30 of thepresent invention, in the step for forming the absorber film 24, theabsorber film 24 is formed by reactive sputtering using a sputteringtarget composed of a material contained in the absorber film 24, and theabsorber film 24 is preferably formed so that a component contained inthe atmospheric gas during reactive sputtering is contained therein. Theflow rate of atmospheric gas during deposition by reactive sputteringcan be adjusted so as to obtain the aforementioned prescribedrelationship between bearing area (%) and bearing area (nm) and theprescribed range of maximum height (Rmax) on the surface of the maskblank multilayer film 26 containing the absorber film 24.

When forming the absorber film 24 by reactive sputtering, theatmospheric gas is preferably a mixed gas containing an inert gas andnitrogen gas. In this case, because the flow rate of nitrogen can beadjusted, the absorber film 24 can be obtained having a suitablecomposition. As a result, the absorber film 24, having theaforementioned prescribed relationship between bearing area (%) andbearing area (nm) and the prescribed range maximum height (Rmax), can bereliably obtained on the surface of the mask blank multilayer film 26.

In the method of manufacturing the reflective mask blank 30 of thepresent invention, the absorber film 24 is preferably formed using asputtering target of a material containing tantalum. As a result, theabsorber film 24 that contains tantalum and has suitable absorption ofexposure light can be obtained.

In the method of manufacturing the reflective mask blank 30 of thepresent invention, in the step for forming the absorber film 24, theabsorber film 24 is formed by sputtering using a sputtering target of anabsorber film material, and materials and composition are selected sothat the surface of the absorber film 24 is such that the maximum height(Rmax) is not more than 4.5 nm, and in the relationship between bearingarea (%) and bearing depth (nm), obtained by measuring a 1 μm×1 μmregion on the surface thereof with an atomic force microscope, when abearing area of 30% is defined as BA₃₀, a bearing area of 70% is definedas BA₇₀, and bearing depths corresponding to a bearing area of 30% andbearing area of 70% are defined as BD₃₀ and BD₇₀, respectively, thesurface of the reflective mask blank is such that(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) is not less than 60(%/nm). The material of theaforementioned absorber film 24 is selected from the previouslyexemplified materials, and the film thickness of the absorber film 24 isset to a film thickness required to have a desired reflectancedifference between light reflected by the multilayer reflective film 21and the protective film 22 and light reflected by the absorber pattern27. The film thickness of the absorber film 24 is preferably set to arange of not more than 60 nm.

The method of manufacturing the reflective mask blank 30 of the presentinvention preferably further comprises a step for forming the protectivefilm 22 arranged in contact with the surface of the multilayerreflective film 21. Because damage to the surface of the multilayerreflective film 21 can be inhibited when fabricating a transfer mask(EUV mask) by forming the protective film 22, reflectance propertieswith respect to EUV light can be further improved. In addition, in themanufactured reflective mask blank 30, detection of pseudo defects onthe surface of the protective film 22 can be inhibited in a defectinspection using a highly sensitive defect inspection apparatus, therebymaking it possible to make critical defects more conspicuous.

The protective film 22 is preferably formed by ion beam sputtering inwhich a sputtering target of the material of the protective film 22 isirradiated with an ion beam. Because smoothing of the protective filmsurface is obtained by ion beam sputtering, the surface of the absorberfilm 24 formed on the protective film 22 and the etching mask film 25further formed on the absorber film 24 can be smoothened.

The method of manufacturing the reflective mask blank 30 of the presentinvention preferably further comprises a step for forming the etchingmask 25 arranged in contact with the surface of the absorber film 24. Byforming the etching mask film 25 to have different dry etchingproperties than those of the absorber film 24, a highly precise transferpattern can be formed when forming a transfer pattern on the absorberfilm 24.

[Reflective Mask 40]

The following provides an explanation of the reflective mask 40according to one embodiment of the present invention.

FIG. 4 is a schematic diagram showing the reflective mask 40 of thepresent embodiment.

The reflective mask 40 of the present invention employs a configurationin which the absorber pattern 27 is formed on the aforementionedmultilayer reflective film 21 or the aforementioned protective film 22by pattering the absorber film 24 on the aforementioned reflective maskblank 30. When the reflective mask 40 of the present embodiment isexposed with exposure light such as EUV light, the exposure light isabsorbed at the portion of the mask surface where the absorber film 24is present, and the exposure light is reflected by the exposedprotective film 22 and the multilayer reflective film 21 at otherportions where the absorber film 24 has been removed. Therefore, thereflective mask 40 of the present embodiment can be used as a reflectivemask 40 for lithography. According to the reflective mask 40 of thepresent invention, detection of pseudo defects in a defect inspectionusing a highly sensitive defect inspection apparatus can be inhibitedand critical defects can be made more conspicuous.

[Method of Manufacturing Semiconductor Device]

A semiconductor device, having various transfer patterns formed on atransferred substrate such as a semiconductor substrate, can bemanufactured by transferring a transfer pattern, such as a circuitpattern, based on the absorber pattern 27 of the reflective mask 40, toa resist film formed on a transferred substrate such as a semiconductorsubstrate by using the previously explained reflective mask 40 and alithography process using an exposure apparatus, followed by goingthrough various other steps.

According to the method of manufacturing a semiconductor device of thepresent invention, because the reflective mask 40, which contaminants,scratches and other critical defects have been removed, can be used in adefect inspection using a highly sensitive defect inspection apparatus,there are no defects in the transfer pattern, such as a circuit pattern,transferred to a resist film formed on a transferred substrate such as asemiconductor substrate, and a semiconductor device can be manufacturedhaving a fine and highly precise transfer pattern.

Furthermore, fiducial marks can be formed on the previously describedmask blank substrate 10, the substrate with a multilayer reflective film20 or the reflective mask blank 30, and the coordinates of the locationsof these fiducial marks and critical defects detected with a highlysensitive defect inspection apparatus as previously described can bemanaged. When fabricating the reflective mask 40 based on the resultingcritical defect location information (defect data), drawing data can becorrected and defects can be reduced so that the absorber pattern 27 isformed at those locations where critical defects are present based onthe aforementioned defect data and transferred pattern (circuit pattern)data.

EXAMPLES

The following provides an explanation of examples of manufacturing thereflective mask blank 30 and the reflective mask 40 according to thepresent embodiment.

First, the multilayer reflective film 21 and the absorber film 24 weredeposited on the surface of the mask blank substrate 10 for EUV exposurein the manner described below to manufacture the substrate with amultilayer reflective film 20 of Example Samples 1 to 5 and ComparativeExample Samples 1 to 4.

<Fabrication of Mask Blank Substrate 10>

An SiO₂—TiO₂-based glass substrate having a size of 152 mm×152 mm and athickness of 6.35 mm was prepared for use as the mask blank substrate10, and the front and back surfaces of the glass substrate weresequentially polished with cerium oxide abrasive particles and colloidalsilica abrasive particles using a double-sided polishing apparatusfollowed by treating the surfaces with a low concentration ofhydrofluorosilicic acid. Measurement of the surface roughness of theresulting glass substrate surface with an atomic force microscopeyielded a root mean square roughness (Rms) of 0.5 nm.

The surface morphology (surface form, flatness) and total thicknessvariation (TTV) of regions measuring 148 mm×148 mm on the front and backsurfaces of the glass substrate were measured with a wavelength-shiftinginterferometer using a wavelength-modulating laser. As a result, theflatness of the front and back surfaces of the glass substrate was 290nm (convex shape). The results of measuring the surface morphology(flatness) of the glass substrate surface were stored in a computer inthe form of height information with respect to a reference surface foreach measurement point, compared with a reference value of 50 nm (convexshape) for the flatness of the front surface and a reference value of 50nm for the flatness of the back side required by glass substrates, andthe differences therewith (required removal amounts) were calculated bycomputer.

Next, processing conditions for local surface processing were setcorresponding to the required removal amounts for each processingspot-shaped region on the surface of the glass substrate. A dummysubstrate was used and preliminarily processed at a spot in the samemanner as actual processing without moving the substrate for a fixedperiod of time, the morphology thereof was measured with the samemeasuring instrument as the apparatus used to measure the surfacemorphology of the aforementioned front and back surfaces, and theprocessing volume of the spot per unit time was calculated. The scanningspeed during Raster scanning of the glass substrate was then determinedin accordance with the required removal amount obtained from the spotinformation and surface morphology information of the glass substrate.

Surface morphology was adjusted by carrying out local surface processingtreatment in accordance with the set processing conditions bymagnetorheological finishing (MRF) using a substrate finishing apparatusemploying a magnetorheological fluid so that the flatness of the frontand back surfaces of the glass substrate was not more than theaforementioned reference values. Furthermore, the magnetorheologicalfluid used at this time contained an iron component, and the polishingslurry used an alkaline aqueous solution containing about 2% by weightof an abrasive in the form of cerium oxide. Subsequently, the glasssubstrate was immersed in a cleaning tank containing an aqueoushydrochloric acid solution having a concentration of about 10%(temperature: about 25° C.) for about 10 minutes followed by rinsingwith pure water and drying with isopropyl alcohol (IPA).

Furthermore, the local processing method employed for the mask blanksubstrate 10 in the present invention is not limited to theaforementioned magnetorheological finishing. A processing method usinggas cluster ion beams (GCIB) or localized plasma may also be used.

Subsequently, surface processing by catalyst-referred etching (CARE) wascarried out after carrying out double-sided touch polishing usingcolloidal silica abrasive particles as the finishing polishing of localsurface processing treatment for the purpose of improving surfaceroughness. This CARE was carried out under the processing conditionsindicated below.

Machining fluid: Pure water

Catalyst: Platinum

Substrate rotating speed: 10.3 rpm

Catalyst surface plate rotating speed: 10 rpm

Processing time: 50 minutes

Processing pressure: 250 hPa

Subsequently, after scrubbing the edge faces of the glass substrate, theglass substrate was immersed in a cleaning tank containing aqua regia(temperature: about 65° C.) for about 10 minutes followed by rinsingwith pure water and drying. Furthermore, cleaning with aqua regia wascarried out several times until there was no longer any Pt catalystresidue on the front and back surfaces of the glass substrate.

When a 1 μm×1 μm region at an arbitrary location of the transfer patternformation region (132 mm×132 mm) on a main surface of the mask blanksubstrate 10 for EUV exposure obtained in the manner described above wasmeasured with an atomic force microscope, root mean square roughness(Rms) was determined to be 0.040 nm and surface roughness maximum height(Rmax) was determined to be 0.40 mm.

As a result of measuring a 1 μm×1 μm region on a main surface of theaforementioned mask blank substrate 10 for EUV exposure, bearing depthBD₃₀ corresponding to a bearing area of 30% (BA₃₀) was 0.322 nm. Inaddition, bearing depth BD₇₀ corresponding to a bearing area of 70%(BA₇₀) was 0.410 nm. Substituting these values into(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) yields the result of(70−30)/(0.410−0.322)=455(%/nm).

A 132 mm×132 mm region on a main surface of the aforementioned maskblank substrate 10 for EUV exposure was inspected for detects using ahighly sensitive defect inspection apparatus having an inspection lightsource wavelength of 193 nm (“Teron 610” manufactured by KLA-TencorCorp.) under inspection sensitivity conditions that enabled detection ofdefects having a size of 21.5 nm in terms of sphere equivalent volumediameter (SEVD). As a result, the total number of defects, includingpseudo defects, detected was 370, and pseudo defects were inhibitedsignificantly in comparison with the more than 50,000 defectsconventionally detected. A number of detected defects of this degree(370 total defects detected) enables the presence of contaminants,scratches or other critical defects to be inspected easily.

In addition, as a result of inspecting a 132 mm×132 mm region on a mainsurface of the aforementioned mask blank substrate 10 for EUV exposurefor defects using a highly sensitive defect inspection apparatus havingan inspection light source wavelength of 266 nm (MAGICS M7360manufactured by Lasertec Corp.) under the most sensitive inspectionconditions, the number of defects, including pseudo defects, was lessthan 50,000 in all cases, thereby enabling inspection of criticaldefects.

Example Samples 1 to 5 and Comparative Example Samples 1 to 4

The multilayer reflective film 21 was formed on the previously describedglass substrate by alternately laminating a Mo layer (low refractiveindex layer, thickness: 2.8 nm) and a Si layer (high refractive indexlayer, thickness: 4.2 nm) (for a total of 40 laminated pairs) by ionbeam sputtering using a Mo target and Si target. When depositing themultilayer reflective film 21 by ion beam sputtering, the incident angleof sputtered Mo and Si particles relative to the normal of a mainsurface of the glass substrate in ion beam sputtering was 30 degrees andion source gas flow rate was 8 sccm.

After depositing the multilayer reflective film 21, an Ru protectivefilm 22 (film thickness: 2.5 nm) was deposited by ion beam sputtering onthe multilayer reflective film 21 in continuation therefrom to obtainthe substrate with a multilayer reflective film 20. When depositing theRu protective film 22 by ion beam sputtering, the incident angle of Rusputtered particles relative to the normal of a main surface of thesubstrate was 40 degrees and the ion source gas flow rate was 8 sccm.

Next, the absorber film 24 was deposited on the surface of thepreviously described protective film 22 of the substrate with amultilayer reflective film 20 by DC magnetron sputtering. In the case ofExample Samples 1 to 4 and Comparative Example Samples 1 to 3, a singlelayer of a TaN film was used for the absorber film 24 as indicated inTable 1. In the case of Example Sample 5 and Comparative Example Sample4, a multilayer film composed of two layers consisting of an absorbinglayer in the form of a TaBN film and a lowly reflecting layer in theform of a TaBO film was used for the absorber film 24 as indicated inTable 2.

The method used to deposit the absorber film 24 (TaN film) of ExampleSamples 1 to 4 and Comparative Example Samples 1 to 3 is as describedbelow. Namely, a TaN film was deposited on the surface of the protectivefilm 22 of the substrate with a multilayer reflective film 20, aspreviously described, by DC magnetron sputtering. More specifically, aTa target (multi-axis rolled target) was placed opposite the surface ofthe protective film 22 of the substrate with a multilayer reflectivefilm 20, and reactive sputtering was carried out in a mixed gasatmosphere of Ar gas and N₂ gas. Table 1 indicates the flow rates of Argas and N₂ gas and other deposition conditions during deposition of theTaN films of Example Samples 1 to 4 and Comparative Example Samples 1 to3. Following deposition, the elementary compositions of the TaN filmswere measured by X-ray photoelectron spectroscopy (XPS). Table 1 showsthe elementary compositions of the TaN films of Example Samples 1 to 4and Comparative Example Samples 1 to 3 as measured by XPS along with thefilm thicknesses of the TaN films. Furthermore, when the crystalstructure of the aforementioned TaN films was measured with an X-raydiffraction (XRD) analyzer, they were determined to have amicrocrystalline structure. The absorber films 24 (TaN films) of ExampleSamples 1 to 4 and Comparative Example Samples 1 to 3 were deposited inthe manner described above.

The method used to deposit the absorber film 24 (multilayer filmcomposed of two layers consisting of an absorbing layer in the form of aTaBN film and a low reflecting layer in the form of a TaBO film) ofExample Sample 5 and Comparative Example Sample 4 is as described below.Namely, an absorbing layer in the form of a TaBN film was deposited byDC magnetron sputtering on the surface of the protective film 22 of thesubstrate with a multilayer reflective film 20 that was previouslydescribed. The TaBN film was deposited by placing the substrate with amultilayer reflective film 20 opposite a TaB mixed sintered target(Ta:B=80:20, atomic ratio) and carrying out reactive sputtering in amixed gas atmosphere of Ar gas and N₂ gas. Table 2 indicates the flowrates of Ar gas and N₂ gas and other deposition conditions duringdeposition of the TaBN films of Example Sample 5 and Comparative ExampleSample 4. Following deposition, elementary compositions of the TaBNfilms were measured by X-ray photoelectron spectroscopy (XPS). Table 2indicates the elementary compositions of the TaBN films of ExampleSample 5 and Comparative Example Sample 4 as measured by XPS along withthe film thicknesses of the TaBN films. Furthermore, when the crystalstructure of the aforementioned TaBN films was measured with an X-raydiffraction (XRD) analyzer, they were determined to have an amorphousstructure.

In the Example Sample 5 and Comparative Example Sample 4, a TaBO film(low reflecting layer) containing Ta, B and O was then further formed onthe TaBN film by DC magnetron sputtering. Similar to the TaBN film ofthe first film, this TaBO film was deposited by placing the substratewith a multilayer reflective film 20 opposite a TaB mixed sinteredtarget (Ta:B=80:20, atomic ratio) and carrying out reactive sputteringin a mixed gas atmosphere of Ar and O₂. Table 2 indicates the flow ratesof Ar gas and O₂ gas and other deposition conditions during depositionof the TaBO films of Example Sample 5 and Comparative Example Sample 4.Following deposition, elementary compositions of the TaBO films weremeasured by X-ray photoelectron spectroscopy (XPS). Table 2 indicatesthe elementary compositions of the TaBO films of Example Sample 5 andComparative Example Sample 4 as measured by XPS along with the filmthicknesses of the TaBO films. Furthermore, when the crystal structureof the aforementioned TaBO films was measured with an X-ray diffraction(XRD) analyzer, they were determined to have an amorphous structure. Theabsorber films 24 (laminated films) of Example Sample 5 and ComparativeExample Sample 4 were deposited in the manner described above.

TABLE 1 Comparative Comparative Comparative Example Example ExampleExample Example Example Example Sample 1 Sample 2 Sample 3 Sample 4Sample 1 Sample 2 Sample 3 Target material Ta Ta Ta Ta Ta Ta TaDeposition Ar (sccm) 20 39 30 20 20 1 40 gas N₂ (sccm) 33 8 20 33 33 605 Film composition (XPS) TaN film TaN film TaN film TaN film TaN filmTaN film TaN film Ta (at %) 50 85 70 50 50 42 92 N (at %) 50 15 30 50 5058 8 Film thickness (nm) 100 100 100 50 200 100 100 Maximum height of3.69 3.41 3.11 2.86 9.14 4.72 4.55 surface roughness Rmax (nm) (BA₇₀ −BA₃₀)/(BD₇₀ − BD₃₀) 112.3 120.2 136.7 150.8 76.0 54.5 58.6 (%/nm) No. ofdefects detected 13204 10508 9878 7014 >100000 >100000 71372 (number)

TABLE 2 Comparative Example Example Sample 5 Sample 4 Absorbing Targetmaterial TaB mixed sintered target TaB mixed sintered target layer (Ta:B= 80:20, atomic ratio) (Ta:B = 80:20, atomic ratio) Deposition Ar (sccm)12.4 12.4 gas N₂ (sccm) 6.0 6.0 Film composition (XPS) TaBN layer TaBNlayer Ta (at %) 74.7 74.1 B (at %) 12.1 12.2 N (at %) 13.2 13.7 Filmthickness (nm) 56 186 Low Target material (Same as first film) (Same asfirst film) reflecting Deposition Ar (sccm) 57.0 57.0 layer gas O₂(sccm) 28.6 28.6 Film composition (XPS) TaBO layer TaBO layer Ta (at %)40.7 40.6 B (at %) 6.3 6.2 O (at %) 53.0 53.2 Film thickness (nm) 14 14Total film thickness (nm) 70 200 Maximum height of surface 4.40 4.83roughness Rmax (nm) (BA₇₀-BA₃₀)/(BD₇₀-BD₃₀) 69.2 67.2 (%/nm) No. ofdefects detected 18572 58113 (number)

Regions measuring 1 μm×1 μm at an arbitrary location of the transferpattern formation regions (and more specifically, in the centers of thetransfer pattern formation regions) (132 mm×132 mm) were measured usingan atomic force microscope on the surfaces of the absorber film 24 ofthe reflective mask blanks 30 for EUV exposure obtained in the form ofExample Samples 1 to 5 and Comparative Example Samples 1 to 4. Tables 1and 2 indicate the maximum height of surface roughness (Rmax) obtainedby measuring with an atomic force microscope and the values of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) (%/nm) when a bearing area of 30% is defined asBA₃₀, a bearing area of 70% is defined as BA₇₀, and bearing depthscorresponding to a bearing area of 30% and bearing area of 70% aredefined as BD₃₀ and BD₇₀, respectively.

For reference purposes, FIG. 6 indicates the results of measuringbearing curves of Example Sample 1 and Comparative Example Sample 1. Asshown in FIG. 6, bearing area (%) is plotted on the vertical axis andbearing depth (nm) is plotted on the horizontal axis. For referencepurposes, FIGS. 7 and 8 indicate BA₇₀, BA₃₀, BD₇₀ and BD₃₀ in thebearing curve measurement results of Example Sample 1 and ComparativeExample Sample 1. In the case of Example Sample 1 indicated in FIG. 7,the value of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) was 112.3(%/nm). On the other hand,in the case of the Comparative Example Sample 1 shown in FIG. 8, thevalue of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) was 76.0(%/nm), thus demonstrating alower value in comparison with the case of Example Sample 1.

As indicated in Tables 1 and 2, the values of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) ofthe bearing curves obtained by measuring regions measuring 1 μm×1 μm onthe surface of the absorber films 24 of Example Samples 1 to 5 with anatomic force microscope were not less than 69.2(%/nm). On the otherhand, the values of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) of the bearing curvesobtained by measuring regions measuring 1 μm×1 μm on the surface of theabsorber films 24 of Comparative Example Samples 2 and 3 with an atomicforce microscope were not more than 58.6(%/nm).

Thus, as indicated in Tables 1 and 2, the values of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) of the bearing curves of the surface of theabsorber films 24 of Example Samples 1 to 5 were not less than 60(%/nm).On the other hand, the values of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) of the bearingcurves of the surface of the absorber films 24 of Comparative ExampleSamples 2 and 3 were less than 60(%/nm).

In addition, as shown in Tables 1 and 2, the maximum height (Rmax) ofsurface roughness obtained by measuring regions measuring 1 μm×1 μm onthe surface of the absorber films 24 of Example Samples 1 to 5 with anatomic force microscope was not more than 4.5 nm. On the other hand, themaximum height (Rmax) of surface roughness obtained by measuring regionsmeasuring 1 μm×1 μm on the surface of the absorber films 24 ofComparative Example Samples 1 to 4 with an atomic force microscope wasgreater than 4.5 nm.

Regions measuring 132 mm×132 mm on the surface of the absorber films 24of Example Samples 1 to 5 and Comparative Example Samples 1 to 4 wereinspected for detects under inspection sensitivity conditions enablingdetection of defects having a sphere equivalent volume diameter (SEVD)of 21.5 nm using a highly sensitive defect inspection apparatus havingan inspection light source wavelength of 193 nm (“Teron 610”manufactured by KLA-Tencor Corp.). Furthermore, sphere equivalent volumediameter (SEVD) can be calculated according to the equation:SEVD=2(3S/4πh)^(1/3) when defining (S) to be the area of the defect anddefining (h) to be the defect height. Defect area (S) and defect height(h) can be measured with an atomic force microscope (AFM).

Tables 1 and 2 indicate the number of defects detected, including pseudodefects, in the surface of the absorber films 24 of Example Samples 1 to5 and Comparative Example Samples 1 to 4 as determined by measuring thesphere equivalent volume diameter (SEVD). The maximum total number ofdefects detected in Example Samples 1 to 5 was 18,572 (Example Sample5), indicating that the number of pseudo defects was significantlyinhibited in comparison with the more than 50,000 defects conventionallydetected. A total of 18,572 detected defects means that the presence orabsence of contaminants, scratches and other critical defects can beinspected easily. In contrast, the minimum total number of defectsdetected in Comparative Example Samples 1 to 4 was 58,113 (ComparativeExample Sample 4), indicating that inspections were unable to be carriedout for the presence or absence of contaminants, scratches or othercritical defects.

Fabrication of Reflective Mask Blank 30: Examples 1 and 2 andComparative Examples 1 and 2

Reflective mask blanks 30 of Examples 1 and 2 and Comparative Examples 1and 2 were fabricated under the conditions shown in Table 3. Namely,similar to the cases of Example Samples 1 to 5 and Comparative ExampleSamples 1 to 4, the multilayer reflective film 21 was formed on thesurface of the mask blank substrate 10 for EUV exposure. Subsequently,the protective film 22 was deposited on the surface of the multilayerreflective film 21, and the absorber film 24 shown in Table 3 wasdeposited on the protective film 22. Moreover, the back sideelectrically conductive film 23 was deposited on the mask blanksubstrate 10 to fabricate the reflective mask blanks 30 of Examples 1and 2 and Comparative Examples 1 and 2.

TABLE 3 Comparative Comparative Example 1 Example 2 example 1 example 2Absorber film Same as Same as Example Same as Same as Example SampleSample 5 (TaBN Comparative Comparative 3 (TaN film) layer/TaBO layer)Example Sample Example Sample 2 (TaN film) 3 (TaN film) Absorber filmthickness 85 85 85 85 (nm) Back side electrically CrN film CrN film CrNfilm CrN film conductive film Back side electrically 20 20 20 20conductive film thickness (nm) Rmax (nm) 3.66 4.32 4.84 4.76(BA₇₀-BA₃₀)/(BD₇₀-BD₃₀) 118.4 66.3 52.6 59.2 (%/nm) No. of defectsdetected 8570 19986 >100000 69950 (number)

Furthermore, fiducial marks for managing coordinates of the locations ofthe aforementioned defects were formed with a focused ion beam at 4locations outside the transfer pattern formation region (132 mm×132 mm)on the protective film 22 and the multilayer reflective film 21 of thesubstrate with a multilayer reflective film 20 used in Examples 1 and 2and Comparative Examples 1 and 2.

The back side electrically conductive film 23 was formed in the mannerdescribed below. Namely, the back side electrically conductive film 23was formed by DC magnetron sputtering on the back side of the substratewith a multilayer reflective film 20 used in Examples 1 and 2 andComparative Examples 1 and 2 where the multilayer reflective film 21 wasnot formed. The back side electrically conductive film 23 was formed bypositioning a Cr target opposite the back side of the substrate with amultilayer reflective film 20 and carrying out reactive sputtering in anatmosphere consisting of a mixture of Ar and N₂ gas (Ar:N₂=90%:10%).Measurement of the elementary composition of the back side electricallyconductive film 23 by Rutherford back scattering analysis yielded valuesof 90 at % for Cr and 10 at % for N. In addition, the film thickness ofthe back side electrically conductive film 23 was 20 nm. The reflectivemask blanks 30 of Examples 1 and 2 and Comparative Examples 1 and 2 werefabricated in the manner described above.

Regions measuring 1 μm×1 μm at arbitrary locations of the transferpattern formation regions (132 mm×132) (and more specifically, thecenters of the transfer pattern regions) on the surfaces of the absorberfilms 24 of the reflective mask blanks 30 of Examples 1 and 2 andComparative Examples 1 and 2 were measured with an atomic forcemicroscope. Table 3 indicates the values of the maximum height (Rmax) ofsurface roughness, obtained by measuring with an atomic forcemicroscope, and the values of values of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) (%/nm)when a bearing area of 30% is defined as BA₃₀, a bearing area of 70% isdefined as BA₇₀, and bearing depths corresponding to a bearing area of30% and bearing area of 70% are defined as BD₃₀ and BD₇₀, respectively.

As shown in Table 3, the maximum height (Rmax) of surface roughness,obtained by measuring regions measuring 1 μm×1 μm on the surface of theabsorber film 24 of the reflective mask blanks 30 of Examples 1 and 2with an atomic force microscope, was not more than 4.5 nm. In contrast,the maximum height (Rmax) of surface roughness, obtained by measuringregions measuring 1 μm×1 μm on the surface of the absorber film 24 ofthe reflective mask blank 30 of Comparative Examples 1 with an atomicforce microscope, was greater than 4.5 nm.

As is also shown in Table 3, the values of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)(%/nm) in the bearing curve measurement results of the surface of theabsorber films 24 of Examples 1 and 2 were not less than 60(%/nm). Incontrast, the values of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) (%/nm) in the bearingcurve measurement results of the surface of the absorber films 24 ofComparative Examples 1 and 2 were less than 60 (%/nm).

Regions measuring 132 mm×132 mm on the surfaces of the absorber films 24of Example Samples 1 to 5 and Comparative Example Samples 1 to 4 wereinspected for detects using a highly sensitive defect inspectionapparatus having an inspection light source wavelength of 193 nm (“Teron610” manufactured by KLA-Tencor Corp.) under inspection sensitivityconditions that enabled detection of defects having a size of 21.5 nm interms of sphere equivalent volume diameter (SEVD). Furthermore, sphereequivalent volume diameter (SEVD) can be calculated according to theequation: SEVD=2(3S/4πh)^(1/3) when defining (S) to be the area of thedefect and defining (h) to be the defect height. Defect area (S) anddefect height (h) can be measured with an atomic force microscope (AFM).

Table 3 indicates the number of defects detected, including pseudodefects, in the surface of the absorber films 24 of Examples 1 and 2 andComparative Examples 1 and 2 as determined by measuring the sphereequivalent volume diameter (SEVD). The maximum total number of defectsdetected in Examples 1 and 2 was 19,986 (Example 2), indicating that thenumber of pseudo defects was significantly inhibited in comparison withthe more than 50,000 defects conventionally detected. A total of 19,986detected defects means that the presence or absence of contaminants,scratches and other critical defects can be inspected easily. Incontrast, the minimum total number of defects detected in ComparativeExamples 1 and 2 was 69,950 (Comparative Example 2), indicating thatinspections were unable to be carried out for the presence or absence ofcontaminants, scratches or other critical defects.

<Fabrication of Reflective Mask 40>

The surface of the absorber film 24 of the reflective mask blanks 30 ofExamples 1 and 2 and Comparative Examples 1 and 2 were coated withresist by spin coating and a resist film 25 having a film thickness of150 nm was deposited thereon after going through heating and coolingsteps. Next, a resist pattern was formed by going through desiredpattern drawing and developing steps. An absorber pattern 27 on theprotective film 22 was formed by patterning of absorber film 24 with aprescribed dry etching using the resist pattern as a mask. Furthermore,when the absorber film 24 consists of a TaBN film, dry etching can becarried out with a mixed gas of Cl₂ and He. In addition, when theabsorber film 24 consists of a laminated film composed of two layersconsisting of a TaBN film and a TaBO film, dry etching can be carriedout with a mixed gas of chlorine (Cl₂) and oxygen (O₂) (mixing ratio(flow rate ratio) of chlorine (Cl₂) to oxygen (O₂)=8:2).

Subsequently, the resist film 25 was removed followed by chemicalcleaning in the same manner as previously described to fabricate thereflective masks 40 of Examples 1 and 2 and Comparative Examples 1 and2. Furthermore, the reflective masks 40 were fabricated after correctingdrawing data in the aforementioned drawing step so that the absorberpattern 27 was arranged at locations where critical defects are presentbased on defect data and transferred pattern (circuit pattern), and thedefect data is generated in reference to the aforementioned fiduciarymarks. Defect inspections were carried out on the resulting reflectivemasks 40 of Examples 1 and 2 and Comparative Examples 1 and 2 using ahighly sensitive defect inspection apparatus (“Teron 610” manufacturedby KLA-Tencor Corp.).

Defects were not confirmed during measurement with the highly sensitivedefect inspection apparatus in the case of the reflective masks 40 ofExamples 1 and 2. On the other hand, in the case of the reflective masks40 of Comparative Examples 1 and 2, a large number of defects duringmeasurement with the highly sensitive defect inspection apparatus.

Fabrication of Reflective Mask Blank 30 Having an Absorber Film with aPhase Shift Function Formed Thereon: Examples 3 to 5

The reflective mask blanks 30 of Examples 3 to 5 were fabricated underthe conditions shown in Table 4. Similar to the cases of Example Samples1 to 5 and Comparative Example Samples 1 to 4, the multilayer reflectivefilm 21 was deposited on the surface of the mask blank substrate 10 forEUV exposure. Subsequently, the protective film 22 was deposited on thesurface of the multilayer reflective film 21 and the absorber film 24shown in Table 4 was deposited on the protective film 22. Morespecifically, the absorber film 24 was formed by laminating a tantalumnitride film (TaN film) and a chromium carbooxonitride film (CrCON film)by DC sputtering. The TaN films were formed in the manner indicatedbelow. Namely, TaN films (Ta: 85 at %, N: 15 at %) having the filmthicknesses described in Table 4 were formed by reactive sputtering in amixed gas atmosphere of Ar gas and N₂ gas using a tantalum target. TheCrCON films were formed in the manner indicated below. Namely, CrCONfilms (Cr: 45 at %, C: 10 at %, O: 35 at %, N: 10 at %) having the filmthicknesses described in Table 4 were formed by reactive sputtering in amixed gas atmosphere of Ar gas, CO₂ gas and N₂ gas using a chromiumtarget. Moreover, similar to Examples 1 and 2, the reflective maskblanks 30 of Examples 3 to 5 were fabricated by depositing the back sideelectrically conductive film 23 on the back side of the mask blanksubstrate 10.

TABLE 4 Example 3 Example 4 Example 5 Absorber film lower layer (filmthickness) TaN (54.3 nm) TaN (48.9 nm) TaN (33.4 nm) Absorber film upperlayer (film thickness) CrCON (5 nm) CrCON (10 nm) CrCON (25 nm) Absorberfilm total thickness (nm) 59.3 58.9 58.4 EUV absolute reflectance (%)2.4 2.9 3.6 Rmax (nm) 2.39 2.52 3.30 (BA₇₀-BA₃₀)/(BD₇₀-BD₃₀) (%/nm)150.8 118.6 98.4 No. of defects detected (number) 6254 10094 25212

Regions measuring 1 μm×1 μm in the centers of the transfer patternformation regions on the surfaces of the absorber film 24 of thereflective mask blanks 30 of Examples 3 to 5 were measured with anatomic force microscope, in the same manner as Examples 1 and 2. Table 4indicates the maximum values of surface roughness (maximum height, Rmax)obtained by measuring with an atomic force microscope, and the values of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) when a bearing area of 30% is defined as BA₃₀, abearing area of 70% is defined as BA₇₀, and bearing depths correspondingto a bearing area of 30% and bearing area of 70% are defined as BD₃₀ andBD₇₀, respectively, in the relationship between bearing area (%) andbearing depth (nm).

As shown in Table 4, the maximum height (Rmax), obtained by measuringregions measuring 1 μm×1 μm on the surface of the absorber film 24 ofthe reflective mask blanks 30 of Examples 3 to 5 with an atomic forcemicroscope, was favorable at not more than 4.5 nm.

As is also shown in Table 3, the values of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)(%/nm) of the surface of the absorber films 24 of Examples 3 to 5 werefavorable at not less than 60(%/nm).

A 132 mm×132 mm region on the surface of the absorber films 24 ofExamples 3 to 5 was inspected for detects using a highly sensitivedefect inspection apparatus having an inspection light source wavelengthof 193 nm (“Teron 610” manufactured by KLA-Tencor Corp.) underinspection sensitivity conditions that enabled detection of defectshaving a size of 21.5 nm in terms of sphere equivalent volume diameter(SEVD).

As a result, the number of defects detected on the surface of theabsorber film 24 of Example 3 was the lowest at 6,254, and was followedby the absorber film 24 of Example 4 at 10,094 defects and the absorberfilm 24 of Example 5 at 25,212 defects, thus indicating that the numberof defects detected was at a level that enables the presence or absenceof contaminants, scratches or other critical defects to be easilyinspected.

<Method of Manufacturing Semiconductor Device>

When semiconductor devices were fabricated using the reflective masks 40of the aforementioned Examples 1 to 5 and Comparative Examples 1 and 2and carrying out pattern transfer on a resist film on a transferredsubstrate (a substrate to be transferred), in the form of asemiconductor substrate, using an exposure apparatus followed bypatterning an interconnection layer, semiconductor devices were able tobe fabricated that were free of pattern defects.

Furthermore, in fabricating the previously described substrate with amultilayer reflective film 20 and the reflective mask blank 30, althoughthe multilayer reflective film 21 and the protective film 22 weredeposited on a main surface of the mask blank substrate 10 on the sidewhere a transfer pattern is formed followed by forming the back sideelectrically conductive film 23 on the opposite side from theaforementioned main surface, fabrication is not limited to this manner.The reflective mask blank 30 may also be fabricated by forming the backside electrically conductive film 23 on a main surface of the mask blanksubstrate 10 on the opposite side from the main surface on the side onwhich a transfer pattern is formed, followed by depositing themultilayer reflective film 21 and the protective film 22 on the mainsurface on the side where the transfer pattern is formed, and finallydepositing the absorber film 24 on the substrate with a multilayerreflective film 20 and the protective film 22.

BRIEF DESCRIPTION OF THE REFERENCE SYMBOLS

-   -   10 Mask blank substrate    -   20 Substrate with a multilayer reflective film    -   21 Multilayer reflective film    -   22 Protective film    -   23 Back side electrically conductive film    -   24 Absorber film    -   25 Etching mask film    -   26 Mask blank multilayer film    -   27 Absorber pattern    -   30 Reflective mask blank    -   40 Reflective mask

The invention claimed is:
 1. A reflective mask blank, comprising: a maskblank multilayer film that comprises a multilayer reflective film,obtained by alternately laminating a high refractive index layer and alow refractive index layer, and an absorber film on or above a mainsurface of a mask blank substrate; wherein, in the relationship betweenbearing area (%) and bearing depth (nm) as measured with an atomic forcemicroscope for a 1 μm×1 μm region of the surface of the reflective maskblank on which the mask blank multilayer film is formed, the surface ofthe reflective mask blank satisfies the relationship of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧60(%/nm) and maximum height (Rmax)≦4.5 nm,wherein BA₃₀ is defined as a bearing area of 30%, BA₇₀ is defined as abearing area of 70%, and BD₃₀ and BD₇₀ respectively is defined asbearing depths corresponding to a bearing area of 30% and bearing areaof 70%.
 2. The reflective mask blank according to claim 1, wherein themask blank multilayer film further comprises a protective film arrangedin contact with a surface of the multilayer reflective film on theopposite side from the mask blank substrate.
 3. The reflective maskblank according to claim 1, wherein the mask blank multilayer filmfurther comprises an etching mask film arranged in contact with thesurface of the absorber film on the opposite side from the mask blanksubstrate.
 4. The reflective mask blank according to claim 1, whereinthe absorber film comprises tantalum and nitrogen, and the nitrogencontent is 10 at % to 50 at %.
 5. The reflective mask blank according toclaim 1, wherein the film thickness of the absorber film is not morethan 60 nm.
 6. The reflective mask blank according to claim 1, whereinthe absorber film has a phase shift function by which the phasedifference between light reflected from the surface of the absorber filmand light reflected from the surface of the multilayer reflective filmor protective film, where the absorber film is not formed, has aprescribed phase difference.
 7. A reflective mask having an absorberpattern on the multilayer reflective film, the absorber pattern beingobtained by patterning the absorber film of the reflective mask blankaccording to claim
 1. 8. A method of manufacturing a semiconductordevice, comprising: forming a transfer pattern on a transferredsubstrate by carrying out a lithography process with an exposureapparatus using the reflective mask according to claim
 7. 9. A method ofmanufacturing a reflective mask blank having a mask blank multilayerfilm comprising a multilayer reflective film and an absorber film on orabove a main surface of a mask blank substrate, wherein a multilayerreflective film is obtained by alternately laminating a high refractiveindex layer and a low refractive index layer, the method comprising:forming the multilayer reflective film on or above the main surface ofthe mask blank substrate, and forming the absorber film on or above themultilayer reflective film; wherein, the flow rate of atmospheric gas iscontrolled so that, in the relationship between bearing area (%) andbearing depth (nm), as measured with an atomic force microscope for a1×μm×1 μm region of the surface of the reflective mask blank on whichthe mask blank multilayer film is formed, the surface of the reflectivemask blank satisfies the relationship of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧60(%/nm) and maximum height (Rmax)≦4.5 nm,wherein BA₃₀ is defined as a bearing area of 30%, BA₇₀ is defined as abearing area of 70%, and BD₃₀ and BD₇₀ respectively is defined asbearing depths corresponding to a bearing area of 30% and bearing areaof 70%.
 10. The method of manufacturing a reflective mask blankaccording to claim 9, wherein the multilayer reflective film is formed,the multilayer reflective film is formed by ion beam sputtering byalternately irradiating a sputtering target of a high refractive indexmaterial and a sputtering target of a low refractive index material withan ion beam.
 11. The method of manufacturing a reflective mask blankaccording to claim 9, wherein, when the absorber film is formed, theabsorber film is formed by reactive sputtering using a sputtering targetof an absorber film material, and the absorber film contains a componentcontained in the atmospheric gas during reactive sputtering.
 12. Themethod of manufacturing a reflective mask blank according to claim 11,wherein the atmospheric gas is a mixed gas containing an inert gas andnitrogen gas.
 13. The method of manufacturing a reflective mask blankaccording to claim 9, wherein the absorber film is formed using asputtering target of a material containing tantalum.
 14. The method ofmanufacturing a reflective mask blank according to claim 9, wherein,when the absorber film is formed, the absorber film is formed bysputtering using a sputtering target of a material of the absorber film,and the material and film thickness of the absorber film are selected sothat the maximum height (Rmax) is not more than 4.5 nm and, in therelationship between bearing area (%) and bearing depth (nm) as measuredwith an atomic force microscope for a 1 μm×1 μm region, the surface ofthe reflective mask blank satisfies the relationship of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀)≧60(%/nm) and maximum height (Rmax)≦4.5 nm,wherein BA₃₀ is defined as a bearing area of 30%, BA₇₀ is defined as abearing area of 70%, and BD₃₀ and BD₇₀ respectively is defined asbearing depths corresponding to a bearing area of 30% and bearing areaof 70%.
 15. The method of manufacturing a reflective mask blankaccording to claim 14, wherein the material of the absorber film is amaterial that contains nitrogen, and the film thickness of the absorberfilm is not more than 60 nm.
 16. The method of manufacturing areflective mask blank according to claim 9, further comprising forming aprotective film arranged in contact with the surface of the multilayerreflective film.
 17. The method of manufacturing a reflective mask blankaccording to claim 16, wherein the protective film is formed by ion beamsputtering by irradiating a sputtering target of a protective filmmaterial with an ion beam.
 18. The method of manufacturing a reflectivemask blank according to claim 9, further comprising forming an etchingmask film arranged in contact with the surface of the multilayerreflective film.